Interleukin-28B Polymorphism Improves Viral Kinetics and Is the Strongest Pretreatment Predictor of Sustained Virologic Response in Genotype 1 Hepatitis C Virus

Article Outline

• Abstract
• Materials and Methods
  • Patients
  • Genotyping
  • Treatment Efficacy Assessments
  • Statistical Analysis
• Results
  • Characteristics of the Study Patients
  • Viral Kinetics
  • Viral Clearance–On-Treatment and SVR
  • SVR Rates According to Week 4 and Week 12 Responses
  • Test Characteristics for IL-28B SNP Genotype Compared With RVR
  • Multivariable Models
  • Analysis of Adherent Patients
• Discussion
• Appendix
• Acknowledgments
• Video Abstract
• Supplementary material
• References
• Copyright

Background & Aims

We recently identified a polymorphism upstream of interleukin (IL)-28B to be associated with a 2-fold difference in sustained virologic response (SVR) rates to pegylated interferon-alfa and ribavirin therapy in a large cohort of treatment-naive, adherent patients with chronic hepatitis C virus genotype 1 (HCV-1) infection. We sought to confirm the polymorphism's clinical relevance by intention-to-treat analysis evaluating on-treatment virologic response and SVR.

Methods

HCV-1 patients were genotyped as CC, CT, or TT at the polymorphic site, rs12979860. Viral kinetics and rates of rapid virologic response (RVR, week 4), complete early virologic response (week 12), and SVR were compared by IL-28B type in 3 self-reported ethnic groups: Caucasians (n = 1171), African Americans (n = 300), and Hispanics (n = 116).

Results

In Caucasians, the CC IL-28B type was associated with improved early viral kinetics and greater likelihood of RVR (28% vs 5% and 5%; P < .0001), complete early virologic response (87% vs 38% and 28%; P < .0001), and SVR (69% vs 33% and 27%; P < .0001) compared with CT and TT. A similar association occurred within African Americans and Hispanics. In a multivariable regression model, CC IL-28B type was the strongest pretreatment predictor of SVR (odds ratio, 5.2; 95% confidence interval, 4.1–6.7). RVR was a strong predictor of SVR regardless of IL-28B type. In non-RVR patients, the CC IL-28B type was associated with a higher rate of SVR (Caucasians, 66% vs 31% and 24%; P < .0001).

Conclusions

In treatment-naive HCV-1 patients treated with pegylated interferon and ribavirin, a polymorphism upstream of IL-28B is associated with increased on-treatment and sustained virologic response and effectively predicts treatment outcome.

Keywords: Genetics, IL-28B, Interferon-Lambda, Peg-Interferon-Alfa

Abbreviations used in this paper: ALT, alanine aminotransferase, BMI, body mass index, cEVR, complete early virologic response, CI, confidence interval, EVR, early virologic response, HCV, hepatitis C virus, HCV-1, hepatitis C virus genotype 1, IL, interleukin, ITT, intention-to-treat, pegIFN, pegylated-interferon, RBV, ribavirin, RVR, rapid virologic response, SNP, single nucleotide polymorphism, SVR, sustained virologic response

One hundred and eighty million individuals worldwide are chronically infected with hepatitis C virus (HCV)¹ and at risk for related morbidity and mortality from cirrhosis and hepatocellular carcinoma. Curative antiviral therapy may prevent these complications. The current standard of care is pegylated-interferon-alfa (pegIFN-alfa) and ribavirin (RBV) combination therapy. However, of patients infected with genotype 1 HCV (HCV-1), the most common HCV genotype in North America, Europe, and Japan, only approximately 40% are cured by standard therapy.², ³, ⁴, ⁵, ⁶ Furthermore, therapy may be associated with considerable toxicity. Therefore, the ability to prospectively identify individual patients who are likely to respond to treatment would be clinically valuable.

A number of pretreatment host and viral factors have been associated with treatment outcome in HCV-1.⁶ These include baseline viral load, age, sex, body mass index (BMI), insulin resistance, hepatic steatosis, and hepatic fibrosis. African American ancestry is a powerful negative predictive factor for sustained virologic response (SVR).⁷, ⁸ The rate of plasma HCV-RNA decline during treatment is predictive of treatment outcome, and virologic responses at week 4 (rapid virologic response [RVR]) and week 12 (early virologic response [EVR]) are additional key therapeutic milestones. However, our understanding of the genetic determinants of treatment outcome has been limited.

We recently performed a genome-wide association study to identify genetic determinants of treatment response in HCV-1 patients treated with pegIFN plus RBV.⁹ We identified a single nucleotide polymorphism (SNP) upstream of the gene IL-28B on chromosome 19, coding for IFN-λ-3, which was associated with an approximately 2-fold difference in SVR rates in patients of European, African American, or Hispanic ancestry.⁹ The analysis was restricted to 1137 of 1671 patients, in which nonresponders were required to have been more than 80% adherent to both pegIFN and RBV dosing, and ethnicity was defined by genetic ancestry.⁹ The importance of this genetic region as a determinant of treatment response has now been confirmed by 2 independent genome-wide association studies.¹⁰, ¹¹ Interleukin (IL)-28B polymorphism also has been shown to be associated with spontaneous clearance after HCV infection.¹², ¹³

In this intention-to-treat (ITT) analysis of the discovery cohort, we sought to interpret the IL-28B polymorphism in a more detailed clinical context to determine how knowledge of this genetic information might impact physician practice. We describe how the genotype of the IL-28B polymorphism influences on-treatment virologic responses, as well as relapse rates, and consider in detail the effect of the polymorphism in the context of other variables predictive of antiviral therapy outcome. Our analyses included all patients, regardless of their level of adherence to therapy, and ethnicity was determined by subject self-report, as it would be in a clinical practice setting.

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Materials and Methods 

Patients 

The study population included 1604 of 3070 patients who were enrolled in the IDEAL study and consented to genetic testing (ClinicalTrials.gov number, NCT00081770).⁶ In addition, 67 patients were included from a second randomized controlled trial.⁷ For all 1671 patients, the protocol-specified treatment duration was 48 weeks, with an additional 24 weeks of follow-up evaluation. Clinical and laboratory data were collected as described previously.⁶, ⁷ Ethnicity was defined by patient self-report, and not genetically inferred ancestry as in the analysis of Ge et al.⁹ A discrepancy between self-report and genetic ancestry was noted in 130 (8%) patients. All patients for whom the polymorphism of interest was genotyped successfully were included in this analysis, which therefore included 491 patients excluded from the analysis by Ge et al⁹ (336 [21%] on the basis of nonadherence).

Genotyping 

A total of 1671 patients were genotyped using the Illumina Human610-quad BeadChip (Illumina, San Diego, CA) as previously described.⁹ We selected the discovery SNP, rs12979860, for this study. Genotype at the polymorphic site rs12979860 on chromosome 19 was suitable for analysis in 1628 patients. For simplicity, we refer to an IL-28B polymorphism throughout this article, noting that the association SNP actually lies 3 kilobases upstream of the IL-28B gene. Genotype was defined as CC, CT, or TT IL-28B type.

Treatment Efficacy Assessments 

HCV-RNA levels were measured using sensitive reverse-transcription polymerase chain reaction assays. In the IDEAL study, the Cobas TaqMan assay (Roche Molecular Diagnostics, Pleasanton, CA) was used, which has a lower limit of quantitation of 27 IU/mL.⁶ In the earlier study by Muir et al,⁷ the NGI SuperQuant assay was used (National Genetics Institute, Culver City, CA), which has a lower limit of quantitation of 39 IU/mL. Viral load was measured at baseline; treatment weeks 2, 4, 12, 24, and 48; and follow-up evaluation weeks 4, 12, and 24 (patients from the study by Muir et al⁷ did not have viral load measured at week 2 or week 4). On-treatment responses were defined by undetectable plasma HCV-RNA levels at the following time points: ultrarapid virologic response at 2 weeks; RVR at 4 weeks; complete EVR (cEVR) at 12 weeks; and end-of-treatment response at 48 weeks.¹⁴ SVR was defined by undetectable HCV-RNA levels at 24 weeks posttreatment (or 12 weeks posttreatment if 24-week follow-up data were not available; n = 40). Relapse was defined as detectable HCV-RNA levels during follow-up evaluation in patients who achieved end-of-treatment response.

Statistical Analysis 

Comparisons between groups were performed using a Wilcoxon test for the non-normal continuous variables, and for categoric data the Pearson chi-square test/Fisher exact test was used. Significance was defined at a P value of less than .05. Analysis of on-treatment response by IL-28B polymorphism was performed in 3 separate ethnic populations: Caucasians, African Americans, and Hispanics (on-treatment responses for the 41 patients of “other” ethnicity are not described). A linear mixed-effects model that included subject-specific intercept and slope and accounted for the left censoring of the viral load measurements was built to analyze the association of IL-28B SNP genotype and race on the log₁₀ viral load within the first 12 weeks of treatment.¹⁵ Multivariable logistic regression with backward elimination was used to identify baseline factors in the entire cohort associated with SVR. Separate models were not constructed for each ethnicity; rather, ethnicity was included as a covariate in the model. Additional covariates considered for inclusion in the model included baseline viral load (log₁₀ IU/mL), fasting blood sugar level, liver fibrosis stage, age, BMI, serum alanine aminotransferase (ALT) level, hepatic steatosis grade, ribavirin starting dose, sex, pegIFN (dose/type), IL-28B type, and IL-28B type by ethnicity interaction. IL-28B polymorphism was evaluated according to CC versus non-CC IL-28B type for the regression modeling. A significance level of 0.05 was used for removal from the model. A second model was built to consider the effect of IL-28B polymorphism for predicting SVR after adjusting for RVR, which included all subjects with measured covariates and virologic data at week 4 (1422 subjects). In addition to the covariates described earlier, we grouped week 4 response and IL-28B polymorphism as a 3-level variable: week 4 responders (RVR); week 4 nonresponders, CC genotype; and week 4 nonresponders, non-CC genotype; there were too few patients without the CC genotype who were also week 4 responders to subset the week 4 responders by genotype. All analyses were performed using R statistical software (R Foundation for Statistical Computing, http://www.R-project.org) and SAS version 9.1 (SAS Institute, Cary, NC).

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Results 

Characteristics of the Study Patients 

A majority of the patients were male (61%) and older than 40 years of age (Table 1). Most patients were Caucasian (72%); African Americans comprised 18% of patients, and Hispanics comprised 7%. Compared with Caucasians, African Americans were older, more likely to have a BMI of 30 kg/m² or greater, and an increased baseline fasting glucose level, and less likely to have an abnormal serum ALT level. Allocation of pegIFN type was balanced between and within each ethnic group. African American patients were less likely to have been assigned an RBV dose greater than 13 mg/kg/day. The frequency of the IL-28B SNP genotype differed between ethnic groups (P < .0001) (Table 1), as previously described.⁹ The CC genotype was observed most frequently in Caucasians (37%), followed by Hispanics (29%) and African Americans (14%). The TT genotype was more common in African Americans (37%) than Hispanics (22%) or Caucasians (12%).

Table 1. Baseline Characteristics of the Clinical Cohort

Baseline characteristics	Caucasians	African Americans	Hispanics	Othera	P valueb
N	1171	300	116	41
Age, y	48(43–52)	51(47–54)	45(39–51)	48(42–53)	<.0001
Age, >40 y	997(85%)	283(94%)	80(69%)	33(80%)	<.0001
Male sex	713(61%)	172(57%)	77(66%)	24(59%)	.2226
BMI	27.4(24.7–30.4)	29.4(26.7–32.6)	28.8(26.0–32.3)	25.5(23.4–28.8)	<.0001
BMI ≥30 kg/m2	328(28%)	138(46%)	44(38%)	9(22%)	<.0001
HCV–RNA level, log10 IU/mL	6.5(6.0–6.8)	6.3(5.9–6.7)	6.2(5.7–6.6)	6.6(6.2–6.9)	.0007
HCV–RNA level, >600,000 IU/mL	979(84%)	244(81%)	83(72%)	35(85%)	.0046
ALT level × ULN (range)	1.7(1.2–2.6)	1.4(1.0–2.0)	2.0(1.3–3.5)	1.7(1.2–2.8)	<.0001
ALT level >ULN	978(84%)	223(74%)	103(88%)	36(85%)	.0002
Fasting glucose level, mmol/L	5.1(4.8–5.6)	5.2(4.7–5.9)	5.1(4.8–5.7)	5.0(4.6–5.4)	.0903
Fasting glucose level, ≥5.6 mmol/L	336(29%)	112(37%)	31(26%)	10(24%)	.0102
Steatosisc
Grade 0	443(40%)	98(35%)	29(25%)	13(35%)	.0006
Grade 1	516(46%)	155(55%)	55(48%)	18(49%)
Grade 2	135(12%)	26(9%)	27(23%)	6(16%)
Grade 3	23(2%)	3(1%)	3(3%)	0(0%)
Grade 4	4(4%)	0(0%)	1(1%)	0(0%)
Steatosis >grade 0	678(60%)	184(65%)	86(74%)	24(65%)	.0059
METAVIR fibrosis stagec
F0	18(2%)	2(1%)	3(3%)	1(3%)	.2091
F1	795(71%)	192(68%)	81(70%)	30(81%)
F2	175(16%)	59(21%)	15(13%)	2(5%)
F3	60(5%)	8(3%)	7(6%)	2(5%)
F4	73(7%)	21(7%)	9(8%)	2(5%)
METAVIR F3–F4	133(12%)	29(10%)	16(14%)	4(11%)	.5715
PegIFN-alfa
2b 1.0 ug/kg/wk	376(32%)	88(29%)	36(31%)	16(42%)	.7612
2b 1.5 ug/kg/wk	417(36%)	118(39%)	45(38%)	4(11%)
2a 180 ug/wk	378(32%)	94(31%)	35(30%)	18(47%)
RBV, mg/kg	13.2(12.4–14.2)	12.8(12.0–13.7)	13.5(12.5–14.7)	14.3(12.6–15.7)	<.0001
RBV >13 mg/kg	649(55%)	123(41%)	70(61%)	29(71%)	<.0001
rs12979860 genotype frequency
CC	436(37%)	42(14%)	34(29%)	26(63%)	<.0001
CT	596(51%)	146(49%)	56(48%)	13(32%)
TT	139(12%)	112(37%)	26(22%)	2(5%)

NOTE. Data are presented as either median (25^th-75^th percentile), or n (%).

ULN, upper limit of normal.

Viral Kinetics 

As previously reported, a small but statistically significant difference in median viral load at baseline was noted according to IL-28B type, with higher levels present in CC patients (Caucasians, 6.6 (6.1–6.9) vs 6.4 (6.0–6.7) vs 6.3 (5.9–6.6) log₁₀ IU/mL for CC, CT, and TT patients, respectively, Supplementary Table 1).⁹ However, when viral load was considered according to the threshold of 600,000 IU/mL, the proportion of patients with high baseline viral load did not differ by IL-28B type.

On-treatment, differences in viral load reduction between genotypes were detectable as early as week 2, the earliest time point evaluated (Figure 1; Supplementary Table 2). Among Caucasians, median reductions of viral load at week 2 were as follows: 2.6, 0.9, and 0.6 log₁₀ IU/mL for patients with the CC, CT, and TT IL-28B types, respectively (P < .0005). Despite ongoing viral decline, the difference was of similar magnitude at weeks 4 and 12, corresponding to increased rates of RVR and cEVR in patients with the CC genotype (Figure 2 and Table 2, Table 3). The rate of viral load reduction in African American and Hispanic patients also was more rapid in those with the CC IL-28B type. However, among African American CC patients, the magnitude of viral decline was less than that observed in Caucasian CC patients at all times (weeks 2, 4, and 12; P < .0020; Figure 1, Supplementary Table 2). Linear mixed-effects modeling confirmed that viral load declined more for patients with the CC versus non-CC IL-28B type (delta, 0.6190; 95% confidence interval [CI], 0.5562–0.6817 log₁₀ IU/mL/wk; Supplementary Table 3). This effect was independent of ethnic background, which also was associated with the rate of viral decline. There was no significant difference in the rate of decline between patients with the CT and TT genotypes (P = .1468).

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• Figure 1. 

  Median reductions in viral load from baseline on the basis of IL-28B type. (A) Caucasian, (B) African American, and (C) Hispanic patients. Bars represent 25th and 75th percentiles. P < .001 for all pairwise comparisons of median viral load for CC vs CT or TT using the Wilcoxon 2-sample test (see Supplementary Table 1, Supplementary Table 2).

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• Figure 2. 

  Virologic responses on treatment on the basis of IL-28B type and ethnicity. (A) Caucasian, (B) African American, and (C) Hispanic patients. EOTR, end-of-treatment response. Statistical comparisons are presented in Table 2.

Table 2. Rates of Virologic Response for Caucasian, African American, and Hispanic Populations

Rates of on-treatment response, SVR	Overall	CC	CT	TT	P value
					CC vs CT	CC vs TT	CT vs TT
Caucasians
SVR	535/1171	301/436	196/596	38/139	<.0001	<.0001	.2061
	(46%)	(69%)	(33%)	(27%)
URVR/wk 2	61/1106	48/414	11/562	2/130	<.0001	.0005	1.000
	(6%)	(12%)	(2%)	(2%)
RVR/wk 4	150/1091	115/406	29/556	6/129	<.0001	<.0001	.7930
	(14%)	(28%)	(5%)	(5%)
cEVR/wk 12	599/1089	354/407	210/559	35/123	<.0001	<.0001	.0565
	(55%)	(87%)	(38%)	(28%)
EOTR/wk 48	687/998	345/374	283/509	59/115	<.0001	<.0001	.4033
	(69%)	(92%)	(56%)	(51%)
Relapse	159/687	48/345	89/283	22/59	<.0001	<.0001	.3835
	(23%)	(14%)	(31%)	(37%)
African Americans
SVR	57/300	20/42	22/146	15/112	<.0001	<.0001	.7035
	(19%)	(48%)	(15%)	(13%)
URVR/wk 2	5/252	3/33	1/124	1/95	.0295	.0524	1.000
	(2%)	(9%)	(1%)	(1%)
RVR/wk 4	11/251	5/33	4/126	2/92	.0195	.0138	1.000
	(4%)	(15%)	(3%)	(2%)
cEVR/wk 12	69/269	19/38	26/133	24/98	.0002	.0041	.3675
	(26%)	(50%)	(20%)	(24%)
EOTR/wk 48	82/250	26/37	32/122	24/91	<.0001	<.0001	.9811
	(33%)	(70%)	(26%)	(26%)
Relapse	26/82	6/26	11/32	9/24	.3471	.2662	.8091
	(32%)	(23%)	(34%)	(38%)
Hispanics
SVR	47/116	19/34	21/56	7/26	.0888	.0249	.3473
	(41%)	(56%)	(38%)	(27%)
URVR/wk 2	11/109	6/31	3/54	2/24	.0675	.4429	.6405
	(10%)	(19%)	(6%)	(8%)
RVR/wk 4	18/111	10/30	6/55	2/26	.0115	.0197	1.000
	(16%)	(33%)	(11%)	(8%)
cEVR/wk 12	54/104	23/29	24/51	7/24	.0048	.0002	.1421
	(52%)	(79%)	(47%)	(29%)
EOTR/wk 48	58/100	24/28	26/49	8/23	.0038	.0001	.1475
	(58%)	(86%)	(53%)	(35%)
Relapse	11/58	4/24	6/26	1/8	.7278	1.000	1.000
	(19%)	(17%)	(23%)	(13%)

NOTE. Data for SVR include the entire ITT population. Data for on-treatment virologic milestones/relapse rates refer to the number of patients who had the evaluation performed. The trial protocol included a stopping rule for patients who did not attain EVR at week 12 (no EVR = reduction of serum HCV RNA <2 log₁₀ IU at week 12).

EOTR, end-of-treatment response at week 48; URVR, ultrarapid virologic response at week 2.

Table 3. Rates of SVR by Week 4, Week 12 Responses

Rates of SVR by wk 4, wk 12 responses	Overall	CC	CT	TT	P value
					CC vs CT	CC vs TT	CT vs TT
Caucasians
RVR	126/150	98/115	22/29	6/6	.2654	.5932	.3113
	(84%)	(85%)	(76%)	(100%)
Non-RVR	388/941	193/291	165/527	30/123	<.0001	<.0001	.1316
	(41%)	(66%)	(31%)	(24%)
cEVR	473/599	288/354	158/210	27/35	.0842	.5456	.8083
	(79%)	(81%)	(75%)	(77%)
Partial EVR	58/280	11/40	37/191	10/49	.2493	.4331	.8704
	(21%)	(28%)	(19%)	(20%)
African Americans
RVR	11/11	5/5	4/4	2/2	1.000	1.000	1.000
	(100%)	(100%)	(100%)	(100%)
Non-RVR	43/240	12/28	18/122	13/90	.0008	.0013	.9497
	(18%)	(43%)	(15%)	(14%)
cEVR	45/69	16/19	15/26	14/24	.0577	.0665	.9634
	(65%)	(84%)	(58%)	(58%)
Partial EVR	11/79	4/13	6/41	1/25	.2296	.0382	.2391
	(14%)	(31%)	(15%)	(4%)
Hispanics
RVR	15/18	8/10	5/6	2/2	1.000	1.000	1.000
	(83%)	(80%)	(83%)	(100%)
Non-RVR	32/93	11/20	16/49	5/24	.0844	.0190	.2946
	(34%)	(55%)	(33%)	(21%)
cEVR	41/54	17/23	18/24	6/7	.9391	1.000	1.000
	(76%)	(74%)	(75%)	(86%)
Partial EVR	5/20	1/6	3/9	1/5	.6044	1.000	1.000
	(25%)	(17%)	(33%)	(20%)

NOTE. Data for SVR include the entire ITT population. Data for on-treatment virologic milestones/relapse rates refer to the number of patients who had the evaluation performed. The trial protocol included a stopping rule for patients who did not attain EVR at week 12 (no EVR = reduction of serum HCV RNA <2 log₁₀ IU at week 12).

EOTR, end-of-treatment response at week 48; URVR, ultrarapid virologic response at week 2.

Viral Clearance–On-Treatment and SVR 

Within each ethnic group, the CC IL-28B type was associated with higher on-treatment response rates at all time points (4, 12, and 48 weeks) (Figure 2 and Table 2). In Caucasians who were CC, 87% attained a cEVR, 10% achieved a pEVR, and only 3% did not achieve a 2-log₁₀ IU/mL reduction in viral load at week 12 of treatment.

Within all populations, the CC IL-28B type was associated with a greater than 2-fold increase in SVR compared with the TT IL-28B type. The rate of SVR observed in Caucasians with the CC IL-28B type (69%) was higher than in either African Americans (48%) or Hispanics (56%) (P = .0079). The CT IL-28B type consistently was associated with numerically higher virologic responses than TT; however, the differences were small and not statistically significant (Figure 2 and Table 2). A detailed description of the SVR rates for each genotype of the IL-28B polymorphism on the basis of individual and combinations of baseline characteristics and week 4 and week 12 on-treatment responses is presented in Supplementary Table 4.

SVR Rates According to Week 4 and Week 12 Responses 

The CC IL-28B type increased the proportion of patients who attained RVR; in those who achieved this key therapeutic milestone, SVR rates were high, independent of IL-28B SNP genotype (Table 3). In contrast, in patients who did not achieve RVR, the effect of IL-28B SNP genotype was strikingly different—SVR rates were significantly higher in patients with the CC IL-28B type in all populations (Caucasian non-RVR:SVR = 66% for CC vs 31% for CT vs 24% for TT; P < .0001). In patients who were CC at the polymorphic site, the rate of cEVR was high in all populations (Table 2). Rates of SVR were higher post-cEVR than in patients attaining only pEVR, but the predictive utility of the IL-28B polymorphism was not strong once week 12 virologic response was available (Table 3).

Test Characteristics for IL-28B SNP Genotype Compared With RVR 

The performance of the IL-28B SNP genotype (CC vs non-CC) as a binary predictor for SVR was evaluated in the 3 major population groups (Table 4). In Caucasian patients, having the CC IL-28B type was more sensitive and had a higher negative predictive value for SVR than RVR; however, RVR had superior positive predictive value and specificity for SVR. Importantly, the CC IL-28B type was present in 37% of the Caucasian population, whereas only 14% attained an RVR. A similar pattern was observed in African American and Hispanic patients.

Table 4. IL-28B Type Versus RVR for Predicting SVR

Overall cohort		Sensitivity, %	Specificity, %	PPV, %	NPV, %
Caucasians	CC vs non-CC (n = 1171)	56(52–60)	79(76–82)	69(65–74)	68(65–71)
	RVR vs no RVR (n = 1091)	25(21–29)	96(94–97)	84(77–89)	59(56–62)
African Americans	CC vs non-CC (n = 300)	35(23–49)	91(86–94)	48(32–63)	86(81–90)
	RVR vs no RVR (n = 251)	20(11–34)	100(98–100)	100(68–100)	82(77–87)
Hispanics	CC vs non-CC (n = 116)	40(27–56)	78(66–87)	56(38–72)	66(54–76)
	RVR vs no RVR (n = 111)	32(20–47)	95(86–99)	83(58–96)	66(55–75)

NOTE. Test performance characteristics presented are for the use of IL-28B type (CC vs non-CC) or RVR (yes/no) as a binary predictor of SVR within each ethnic population. Data shown are the test statistic (95% CI).

PPV, positive predictive value; NPV, negative predictive value.

Multivariable Models 

Regression modeling was used to identify pretreatment factors that were associated independently with SVR. Data from 1550 patients with a complete dataset of the covariates of interest were included in the model. We first modeled SVR considering all predictors as dichotomous variables (continuous and ordinal variables were dichotomized according to clinically relevant thresholds⁶). Multivariable logistic regression using backward selection identified IL-28B type, ethnic background, baseline viral load, hepatic fibrosis stage, and fasting glucose level as being associated independently with SVR (Table 5). IL-28B type had the greatest odds ratio favoring SVR in this model (CC vs non-CC: odds ratio, 5.2; 95% CI, 4.1–6.7; P < .0001). A second multivariate logistic regression model was built in which continuous and ordinal variables were not dichotomized, allowing us to use pseudo R-squared values to estimate the contribution of each variable to the variability observed in SVR. IL-28B type (CC vs non-CC) was estimated to explain 14.8% of the variability in treatment response in the cohort, after adjustment for the other independent predictors (Supplementary Table 5). Other independent predictors of SVR in this more powerful model included ethnic background, baseline viral load, hepatic fibrosis stage, fasting glucose level, BMI, and RBV starting dose (mg/kg). No other predictor explained more than 5% of the variability in SVR, and the IL-28B type therefore was the strongest pretreatment predictor of SVR.

Table 5. Multivariable Logistic Regression Models for SVR

	Odds ratio	95% CI	P value
Model 1: baseline variables only
CC IL-28B type vs non-CC	5.2	4.1–6.7	<.0001
HCV RNA ≤600,000 vs >600,000 IU/mL	3.1	2.3–4.1	<.0001
Caucasian vs AA ethnicity	2.8	2.0–4.0	<.0001
Hispanic vs AA ethnicity	2.1	1.3–3.6	.0041
METAVIR F0–2 vs F3–4	2.7	1.8–4.0	<.0001
Fasting blood sugar level <5.6 vs ≥5.6 mmol/L	1.7	1.3–2.2	<.0001
Model 2: considering IL-28B type and RVR in the same model
RVR vs (non-RVR + non-CC)	9.1	5.8–14.0	<.001
(Non-RVR + CC) vs (non-RVR + non-CC)	5.2	3.9–6.9	<.001
METAVIR F0–2 vs F3–4	2.7	1.7–4.1	<.001
HCV RNA ≤600,000 vs >600,000 IU/mL	2.4	1.7–3.4	<.001
Caucasian vs AA ethnicity	2.3	1.6–3.3	<.001
Hispanic vs AA ethnicity	1.8	1.04–3.1	.0361
Fasting blood sugar level <5.6 vs ≥5.6 mmol/L	1.7	1.3–2.3	.0001

NOTE. Model 1: the baseline model considered IL-28B-type (CC vs non-CC) and the following covariates, previously identified to be associated independently with SVR in the IDEAL study population⁶: ethnic background, age (±40 y), sex, BMI (±30 kg/m²), baseline HCV–RNA level (±600,000 IU/mL), ALT level (±ULN), fasting glucose level (±5.6 mmol/L), hepatic steatosis (absent vs present), hepatic fibrosis stage (METAVIR F0–2 vs F3–4), and RBV dose (±13 mg/kg/day). PegIFN type was not associated with SVR in univariable analysis (Supplementary Table 11). Variables not present in the final model were removed by backward selection. A significance level of 0.05 was used for removal from the model. Model 2: the week-4 model collapsed the week-4 response and IL-28B polymorphism as a 3-level variable (RVR vs non-RVR + CC IL-28B type vs non-RVR + non-CC IL-28B type). Otherwise, the same covariates were included as for the baseline model.

A second important question relates to the informativeness of IL-28B status after viral response at week 4 is known. For those subjects attaining RVR, IL-28B type was not associated with SVR (CC vs non-CC genotype, P = .6734). However, for those who did not attain RVR, IL-28B type had a strong predictive value (P < .0001). A direct comparison between these 2 groups showed that the predictive value of the IL-28B polymorphism was significantly different (P value for interaction = .0023). A model then was built to consider the independent effects of the IL-28B polymorphism and RVR in the context of the other baseline predictors. RVR had the largest odds ratio for SVR (odds ratio, 9.1; 96% CI, 5.8–14.0 vs non-RVR non-CC genotype reference) (Table 5). In non-RVR patients, CC genotype was associated independently with SVR (odds ratio, 5.2; 95% CI, 3.9–6.9 vs non-CC genotypes). An additional term to divide patients who attained RVR by IL-28B polymorphism was not significant.

Analysis of Adherent Patients 

We also analyzed the 1137 adherent patients used for the genetic association study⁹ (Supplementary Table 6, Supplementary Table 7, Supplementary Table 8, Supplementary Table 9, Supplementary Table 10, Supplementary Figure 1, Supplementary Figure 2). The effect of the IL-28B type on treatment response was similar in this subset. SVR rates were higher, consistent with the role for adherence in treatment outcome.¹⁶

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Discussion 

We previously identified a polymorphism upstream of the IL-28B gene to be associated strongly with SVR in treatment-adherent HCV-1 patients.⁹ In this ITT analysis, we present a number of novel insights. The clinical relevance of the genetic discovery was confirmed, irrespective of the degree of treatment adherence. The polymorphism was associated with improved SVR rates by enhancing early viral kinetics, increasing the rates of week 4, week 12, and week 48 viral clearance, and decreasing the rate of posttreatment relapse. Two major benefits of the polymorphism were observed: (1) a higher rate of RVR, which was followed in most cases by an SVR; and (2) a 2-fold increase in the rate of SVR in the majority of patients (>80%) who did not achieve an RVR. The effect of this polymorphism on treatment response was maintained in Caucasians, African Americans, and Hispanics, in whom the differing allele frequencies contributed very strongly to the racial disparity in overall response rates. Indeed, African American patients with the CC IL-28B type responded better than Caucasian patients with the non-CC IL-28B types. Finally, the strength of this genetic factor as a predictor of treatment response was borne out in the multivariable analysis, where it was the strongest pretreatment predictor of SVR.

The key marker for improved treatment response was the CC IL-28B type. The rate of SVR was doubled in patients with the CC compared with the non-CC IL-28B type in all populations. The CC IL-28B type was associated with improved early viral suppression, such that by week 2 of treatment the median reduction in viral load was 2-log₁₀ IU/mL greater in Caucasian patients with CC versus non-CC genotypes. The more rapid reduction in viral load correlated with increased rates of RVR and cEVR. Relapse rates also were lower in Caucasian and African American patients with the CC IL-28B type.

All patients who attained RVR had a high rate of SVR, although it is important to note that patients with the CC genotype were most likely to reach RVR. In contrast, the IL-28B polymorphism was very important in the non-RVR patients, for whom having a CC genotype increased SVR rates 2-fold. Although viral load sampling was not performed between weeks 4 and 12 of treatment, the viral kinetics predicted that the majority of these CC patients who did not attain an RVR were likely to have become HCV-RNA negative soon after 4 weeks. The weak utility of IL-28B genotype for predicting SVR once the week 12 virologic response was determined, was also consistent with the fact that the major effect of the IL-28B polymorphism was to influence viral kinetics before week 12. Together, these observations emphasize that the major effect of this polymorphism was to increase the rate of early viral decline, leading to higher SVR rates.

The observation that the CC genotype is less frequent in African American patients advances our understanding of the poor response rates seen in this population.⁷, ⁸ However, even in African American patients with the CC genotype, viral kinetics were slower, and rates of RVR, cEVR, and SVR were lower. African American ancestry remained an independent negative predictor of outcome in the multivariable logistic regression. This could suggest the presence of other as yet undetected gene variants that influence treatment response in African Americans compared with Caucasians.

We believe that knowledge of IL-28B type will aid both clinicians and patients in making decisions about pegIFN and RBV therapy. Patients who have the good response CC IL-28B type have a high likelihood of attaining SVR and, in the absence of other concerns regarding suitability for therapy, should be considered ideal candidates. In contrast, patients with the non-CC IL-28B type, especially in the setting of other markers of poor response, such as African American ethnicity, advanced fibrosis, or high viral load, are unlikely to attain SVR. In this setting, the urgency for therapy should be weighed against the expected availability of direct antivirals in the near future.¹⁷

The clinical utility of IL-28B genotyping was compared with that of week 4 viral clearance. Although RVR had a higher positive predictive value for SVR, it cannot be evaluated before therapy and is uncommon in HCV-1 patients. In comparison, the CC genotype, present in 37% of Caucasians, was strongly predictive of SVR, even if RVR was not achieved. It is likely that RVR and IL-28B genotyping will have complementary roles in clinical practice, with IL-28B type having important utility at baseline, and at week 4 for non-RVR patients.

The mechanisms through which IL-28B SNP genotype influences antiviral response to pegIFN and RBV remain unclear. The protein product of IL-28B is IFN-λ-3, 1 of the 3 members of the recently described type 3 IFN family (IFN-λ-1/2/3 = IL-29, IL-28A, and IL-28B).¹⁸, ¹⁹ In experimental models, IFN-λ inhibits both HCV and HBV replication.²⁰ In co-stimulation experiments, IFN-λ and IFN-alfa have an additive antiviral effect.²¹ Antiviral activity of recombinant IFN-λ-1 (IL-29) has been confirmed in HCV-1 patients.²² The discovery is therefore biologically plausible, and suggests the IFN-λ signaling axis as an important new direction for studying natural viral defenses.

The data raise a number of important issues. Future studies should address whether IL-28B SNP genotyping may be used to personalize duration of therapy. Whether the IL-28B polymorphism has a role in predicting treatment outcome with the addition of direct antivirals in future HCV treatment regimens needs to be established. The delayed viral kinetics seen in patients with the non-CC genotypes, apparent as early as treatment week 2, might suggest a particular role for the direct antivirals in these patients. The relevance of the IL-28B polymorphism to non–HCV-1 infection is not known. Finally, because the polymorphism is the strongest baseline factor predictive of response, and profoundly effects viral kinetics as early as week 2, current clinical trials investigating direct antivirals on a pegIFN/RBV backbone should be analyzed by IL-28B type, and stratification of patients will need to be considered in the future to balance treatment arms according to IL-28B type.

In conclusion, IL-28B type is the strongest baseline predictor of SVR to pegIFN plus RBV in treatment-naive patients with HCV-1. The good response CC IL-28B type is associated with improved viral kinetics and increased rates of RVR, cEVR, and end-of-treatment response, as well as reduced relapse. Even in patients who do not attain RVR, the CC IL-28B type is associated with high rates of SVR. The data strongly support a future role for IL-28B SNP genotyping as part of a clinical assessment before standard antiviral therapy in individuals chronically infected with HCV-1.

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Appendix 

Other participants and members of the IDEAL study group included the following: Abdullah Al-Osaimi, Luis Balart, Michael Bennett, David Bernstein, Edmund Bini, Martin Black, Joseph Bloomer, Hector Bonilla, Terry Box, Thomas Boyer, Norbert Brau, Kimberly Brown, Robert Brown, Christine Bruno, William Cassidy, Raymond Chung, David Clain, Jeffrey Crippin, Douglas Dalke, Charles Davis, Gary Davis, Franco Felizarta, Roberto Firpi-Morell, Steven Flamm, Jose Franco, Alexandra Gibas, Eliot Godofsky, Fredric Gordon, John Gross, Stephen Harrison, Jorge Herrera, Steven Herrine, Robert Herring, Ke-Qin Hu, Jonathan Israel, Shobha Joshi, Mandana Khalili, Alan Kilby, Paul King, Alvaro Koch, Edward Krawitt, Marcelo Kugelmas, Louis Lambiase, Edward Lebovics, James Levin, Robert Levine, Steven Lidofsky, Michael Lucey, Mark Mailliard, Luis Marsano, Paul Martin, Thomas McGarrity, Dennis Mikolich, Timothy Morgan, Kevin Mullen, Santiago Munoz, Donald Nelson, Frederick Nunes, Anders Nyberg, Sangik Oh, Prashant Pandya, Mary Pat Pauly, Craig Peine, Robert Perillo, Gary Poleynard, Anthony Post, John Poulos, David Pound, Mordechai Rabinovitz, Natarajan Ravendhran, Joanna Ready, Rajender Reddy, Adrian Reuben, Lorenzo Rossaro, Lawrence Rothman, Raymond Rubin, Vinod Rustgi, Michael Ryan, Warren Schmidt, William Semon, Thomas Sepe, Kenneth Sherman, Maria Sjogren, Robert Sjogren, Coleman Smith, Lawrence Stein, Robert Strauss, Mark Swaim, Gyongnyi Szabo, Joseph Thurn, Myron Tong, John Vierling, George Wu, Rockford Yapp, Ziad Younes, and Atif Zaman.

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Acknowledgments 

The authors are indebted to the IDEAL principal investigators, the study coordinators, nurses, and patients involved in the study (see Appendix). The authors recognize Jennifer King, PhD, for editorial assistance in preparing the manuscript.

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Video Abstract 

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Supplementary material 

Supplementary Table 1. HCV–RNA Levels at Baseline

Baseline HCV–RNA level, log10 IU/mL	CC	CT	TT	P valuea
				CC vs CT	CC vs TT	CT vs TT
Caucasians
N	436	596	139
Median (25th–75th percentile)	6.6(6.1–6.9)	6.4(6.0–6.7)	6.2(5.9–6.5)	<.0001	<.0001	.0012
HCV–RNA level > 600,000 IU/mL, N (%)	367/436(84.2%)	502/596(84.2%)	110/139(79.1%)	.9813	.1690	.1476
African Americans
N	42	146	112
Median (25th–75th percentile)	6.7(6.2–6.9)	6.4(5.9–6.8)	6.2(5.8–6.6)	.0183	<.0001	.0197
HCV–RNA level, >600,000 IU/mL, N (%)	38/42(90.5%)	118/146(80.1%)	88/112(78.6%)	.1423	.0880	.6552
Hispanics
N	34	56	26
Median (25th–75th percentile)	6.5(5.9–6.9)	6.1(5.7–6.5)	6.0(5.4–6.3)	.0160	.0016	.1571
HCV–RNA level > 600,000 IU/mL, N (%)	28/34(82.3%)	39/56(69.6%)	16/26(61.5%)	.1801	.0708	.4674

Supplementary Table 2. Median On-Treatment Reduction of HCV–RNA Levels

Median on-treatment HCV–RNA reduction, log10 IU/mL	CC	CT	TT	P valuea
				CC vs CT	CC vs TT	CT vs TT
Caucasians
Week 2(n = 1106) median (25th–75th percentile)	2.6(1.9–3.4)	0.9(0.4–1.5)	0.6(0.3–1.1)	<.0001	<.0001	.0003
Week 4(n = 1091) median (25th–75th percentile)	3.8(3.0–4.6)	1.5(0.9–2.4)	1.1(0.7–1.8)	<.0001	<.0001	.0003
Week 12(n = 1089) median (25th–75th percentile)	5.5(4.7–5.9)	3.7(1.8–4.9)	3.1(1.7–4.4)	<.0001	<.0001	.0447
African Americans
Week 2(n = 252) median (25th–75th percentile)	1.9(1.0–2.4)	0.7(0.3–1.1)	0.6(0.3–0.9)	<.0001	<.0001	.3013
Week 4(n = 251) median (25th–75th percentile)	2.8(1.5–3.6)	1.1(0.6–1.7)	0.9(0.6–1.7)	<.0001	<.0001	.4004
Week 12(n = 269) median (25th–75th percentile)	4.7(3.4–5.5)	2.0(1.1–4.0)	2.0(0.9–4.2)	<.0001	<.0001	.4957
Hispanics
Week 2(n = 109) median (25th–75th percentile)	2.2(1.6–3.5)	1.0(0.4–2.0)	0.6(0.3–1.1)	<.0001	<.0001	.0963
Week 4(n = 111) median (25th–75th percentile)	3.6(3.0–4.4)	1.6(1.0–3.1)	1.0(0.6–2.1)	<.0001	<.0001	.0503
Week 12(n = 104) median (25th–75th percentile)	5.3(4.3–5.8)	4.1(1.2–5.1)	2.5(1.1–4.0)	.0005	<.0001	.0337

Supplementary Table 3. Linear Mixed Effects Modeling¹⁵ of Viral Kinetics to Week 12 in the Overall Cohort

Parameter	Estimate	95% CI, lower–upper boundary	P value
Week*CC	−0.5872	−0.6328to-0.5416	<.0001
Week*Caucasian	−0.1702	−0.2220to-0.1184	<.0001
Week*Hispanic	−0.1840	−0.2713to-0.0967	<.0001

NOTE. For the comparison of median viral load reductions at weeks 2, 4, and 12 of treatment (Figure 1 and Supplementary Table 1), a value of 10 IU/mL (1 log₁₀ IU/mL) was substituted for HCV–RNA counts that were below the limit of detection (27 IU/mL). This practice of imputing 1 log₁₀ IU/mL for all left-censored values will introduce bias to comparisons between genotypes and races, potentially underestimating effect. To reduce the bias, a linear mixed-effects model for longitudinal left-censored data was fit to the log HCV–RNA data with race and genotype as covariates.¹ The results suggest that HCV–RNA level declined 0.5872 log₁₀ IU/mL/wk more for patients with the CC vs non-CC IL-28B type (95% CI, 0.5416–0.6328). Even after accounting for IL-28B type, race was still a significant factor in the rate of viral decline. On average, Caucasians and Hispanics decreased their HCV–RNA value 0.1702 and 0.1840 log₁₀ IU/mL more per week, respectively, than African Americans (95% CI, 0.1184–0.2220 and 0.0967–0.2713, respectively). African American ethnic background and the non-CC IL-28B type were used as the reference groups. The estimate describes the average difference in the rate of change in the viral load per week compared with the reference group. Week*CC describes the average difference between the slope of patients with the CC IL-28B type vs the non-CC IL-28B types. Week*Caucasian describes the average difference between the slope of African Americans and Caucasians.

Supplementary Table 4. SVR Rates for Each Genotype of the IL-28B Polymorphism in the Overall Cohort, According to Baseline Characteristics and Week 4 and Week 12 On-Treatment Responses

Caucasians	Overall	CC	CT	TT
Overall	535/1171	301/436	196/596	38/139
	(46%)	(69%)	(33%)	(27%)
Baseline factors
Age ≤ 40 y	98/174	47/67	42/86	9/21
	(56%)	(70%)	(49%)	(43%)
Age > 40 y	437/997	254/369	154/510	29/118
	(44%)	(69%)	(30%)	(25%)
Female	209/458	102/148	90/247	17/63
	(46%)	(69%)	(36%)	(27%)
Male	326/713	199/288	106/349	21/76
	(46%)	(69%)	(30%)	(28%)
HCV–RNA level, ≤600,000 IU/mL	130/192	58/69	57/94	15/29
	(68%)	(84%)	(61%)	(52%)
HCV–RNA level, >600,000 IU/mL	405/979	243/367	139/502	23/110
	(41%)	(66%)	(28%)	(21%)
METAVIR F0–2	471/988	263/365	173/505	35/118
	(48%)	(72%)	(34%)	(30%)
METAVIR F3–4	37/133	21/51	14/64	2/18
	(28%)	(41%)	(22%)	(11%)
Fasting glucose level, <5.6 mmol/L	419/835	230/318	159/415	30/102
	(50%)	(72%)	(38%)	(29%)
Fasting glucose level, ≥5.6 mmol/L	116/336	71/118	37/181	8/37
	(35%)	(60%)	(20%)	(22%)
BMI < 30	383/843	206/306	149/430	28/107
	(45%)	(67%)	(35%)	(26%)
BMI ≥ 30	152/328	95/130	47/166	10/32
	(46%)	(73%)	(28%)	(31%)
RBV dose, >13 mg/kg/day	313/649	162/227	124/334	27/88
	(48%)	(71%)	(37%)	(31%)
RBV dose, ≤13 mg/kg/day	222/521	139/208	72/262	11/51
	(43%)	(67%)	(27%)	(22%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	113/164	48/56	51/81	14/27
	(69%)	(86%)	(63%)	(52%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	7/17	5/8	2/8	0/1
	(41%)	(63%)	(25%)	(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	358/824	215/309	122/424	21/91
	(43%)	(70%)	(29%)	(23%)
HCV–RNA level, >600,000 IU/mL and F3–4	30/116	16/43	12/56	2/17
	(26%)	(37%)	(21%)	(12%)
On-treatment responses
RVR	126/150	98/115	22/29	6/6
	(84%)	(85%)	(76%)	(100%)
Non-RVR	388/941	193/291	165/527	30/123
	(41%)	(66%)	(31%)	(24%)
≥4-log reduction in HCV–RNA level at wk 4	173/220	137/175	32/40	4/5
	(79%)	(78%)	(80%)	(80%)
<4-log reduction in HCV– RNA level at wk 4	362/951	164/261	164/556	34/134
	(38%)	(63%)	(30%)	(25%)
cEVR	473/599	288/354	158/210	27/35
	(79%)	(81%)	(75%)	(77%)
Partial EVR	58/280	11/40	37/191	10/49
	(21%)	(28%)	(19%)	(20%)
Combination of wk 4 response + baseline factors
RVR + baseline HCV–RNA level, ≤ 600,000	66/77	47/52	14/20	5/5
	(86%)	(90%)	(70%)	(100%)
RVR + baseline HCV–RNA level, >600,000	60/73	51/63	8/9	1/1
	(82%)	(81%)	(89%)	(100%)
Non-RVR + baseline HCV–RNA level, ≤ 600,000	58/97	9/12	41/64	8/21
	(60%)	(75%)	(64%)	(38%)
Non-RVR + baseline HCV–RNA level, >600,000	330/844	184/279	124/463	22/102
	(39%)	(66%)	(27%)	(22%)
RVR + F0–2	112/135	86/102	20/27	6/6
	(83%)	(84%)	(74%)	(100%)
RVR + F3–4	7/8	7/8	*	*
	(88%)	(88%)
Non-RVR + F0–2	343/792	169/241	147/449	27/102
	(43%)	(70%)	(33%)	(26%)
Non-RVR + F3–4	25/108	12/36	11/54	2/18
	(23%)	(33%)	(20%)	(11%)
RVR + baseline HCV–RNA level, ≤600,000 + F0–2	58/69	40/45	13/19	5/5
	(84%)	(89%)	(68%)	(100%)
RVR + baseline HCV–RNA level, ≤600,000 + F3–4	4/4	4/4	*	*
	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F0–2	54/66	46/57	7/8	1/1
	(82%)	(81%)	(88%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	3/4	3/4	*	*
	(75%)	(75%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F0–2	49/82	6/7	36/56	7/19
	(60%)	(86%)	(64%)	(37%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F3–4	3/9	1/3	2/5	0/1
	(33%)	(33%)	(40%)	(0%)
Non-RVR + baseline HCV–RNA level, >600,000 + F0–2	294/710	163/234	111/393	20/83
	(41%)	(70%)	(28%)	(24%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	22/99	11/33	9/49	2/17
	(22%)	(33%)	(18%)	(12%)
African Americans
Overall	57/300	20/42	22/146	15/112
	(19%)	(48%)	(15%)	(13%)
Baseline factors
Age ≤ 40 y	4/17	1/2	2/11	1/4
	(24%)	(50%)	(18%)	25%)
Age > 40 y	53/283	19/40	20/135	14/108
	(19%)	(48%)	(15%)	(13%)
Female	27/128	9/17	10/61	8/50
	(21%)	(53%)	(16%)	(16%)
Male	30/172	11/25	12/85	7/62
	(17%)	(44%)	(14%)	(11%)
HCV–RNA level, ≤ 600,000 IU/mL	21/56	4/4	8/28	9/24
	(38%)	(100%)	(29%)	(38%)
HCV–RNA level, >600,000 IU/mL	36/244	16/38	14/118	6/88
	(15%)	(42%)	(12%)	(7%)
METAVIR F0–2	51/253	17/35	20/125	14/93
	(20%)	(49%)	(16%)	(15%)
METAVIR F3–4	3/29	1/3	1/14	1/12
	(10%)	(33%)	(7%)	(8%)
Fasting glucose level, <5.6 mmol/L	42/188	15/29	16/90	11/69
	(22%)	(52%)	(18%)	(16%)
Fasting glucose level, ≥5.6 mmol/L	15/112	5/13	6/56	4/43
	(13%)	(38%)	(11%)	(9%)
BMI < 30	25/162	8/21	11/81	6/60
	(15%)	(38%)	(14%)	(10%)
BMI ≥ 30	32/138	12/21	11/65	9/52
	(23%)	(57%)	(17%)	(17%)
RBV dose, >13 mg/kg/day	22/123	8/18	6/56	8/49
	(18%)	(44%)	(11%)	(16%)
RBV dose, ≤13 mg/kg/day	35/176	12/24	16/90	7/62
	(20%)	(50%)	(18%)	(11%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	19/48	3/3	7/22	9/23
	(40%)	(100%)	(32%)	(39%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	0/4	*	0/4	*
	(0%)		(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	32/205	14/32	13/103	5/70
	(16%)	(44%)	(13%)	(7%)
HCV–RNA level, >600,000 IU/mL and F3–4	3/25	1/3	1/10	1/12
	(12%)	(33%)	(10%)	(8%)
On-treatment responses
RVR	11/11	5/5	4/4	2/2
	(100%)	(100%)	(100%)	(100%)
Non-RVR	43/240	12/28	18/122	13/90
	(18%)	(43%)	(15%)	(14%)
≥4-log reduction in HCV–RNA level at wk 4	13/14	7/7	4/5	2/2
	(93%)	(100%)	(80%)	(100%)
<4-log reduction in HCV–RNA level at wk 4	44/286	13/35	18/141	13/110
	(15%)	(37%)	(13%)	(12%)
cEVR	45/69	16/19	15/26	14/24
	(65%)	(84%)	(58%)	(58%)
Partial EVR	11/79	4/13	6/41	1/25
	(14%)	(31%)	(15%)	(4%)
Combination of wk 4 response + baseline factors
RVR + baseline HCV–RNA level, ≤600,000	8/8(100%)	3/3(100%)	3/3(100%)	2/2(100%)
RVR + baseline HCV–RNA level, >600,000	3/3	2/2	1/1	*
	(100%)	(100%)	(100%)	*
Non-RVR + baseline HCV–RNA level, ≤600,000	12/35	*	5/18	7/17
	(34%)		(28%)	(41%)
Non-RVR + baseline HCV–RNA level, >600,000	31/205	12/28	13/104	6/73
	(15%)	(43%)	(13%)	(8%)
RVR + F0–2	10/10	4/4	4/4	2/2
	(100%)	(100%)	(100%)	(100%)
RVR + F3–4	*	*	*	*
Non-RVR + F0–2	39/203	11/24	16/105	12/74
	(19%)	(46%)	(15%)	(16%)
Non-RVR + F3–4	2/22	0/1	1/11	1/10
	(9%)	(0%)	(9%)	(10%)
RVR + baseline HCV–RNA level, ≤600,000 + F0–2	7/7	2/2	3/3	2/2
	(100%)	(100%)	(100%)	(100%)
RVR + baseline HCV–RNA level, ≤600,000 + F3–4	*	*	*	*
RVR + baseline HCV–RNA level, >600,000 + F0–2	3/3	2/2	1/1	*
	(100%)	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	*	*	*	*
Non-RVR + baseline HCV–RNA level, ≤ 600,000 + F0–2	11/30	*	4/14	7/16
	(37%)		(29%)	(44%)
Non-RVR + baseline HCV–RNA level, ≤ 600,000 + F3–4	0/3	*	0/3	*
	(0%)		(0%)
Non-RVR + baseline HCV–RNA level, > 600,000 + F0–2	28/173	11/24	12/91	5/58
	(16%)	(46%)	(13%)	(9%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	2/19	0/1	1/8	1/10
	(11%)	(0%)	(13%)	(10%)
Hispanics
Overall	47/116	19/34	21/56	7/26
	(41%)	(56%)	(38%)	(27%)
Baseline factors
Age ≤ 40 y	13/36	4/10	6/19	3/7
	(36%)	(40%)	(32%)	(43%)
Age > 40 y	34/80	15/24	15/37	4/19
	(43%)	(63%)	(41%)	(21%)
Female	14/39	2/6	9/24	3/9
	(36%)	(33%)	(38%)	(33%)
Male	33/77	17/28	12/32	4/17
	(43%)	(61%)	(38%)	(24%)
HCV–RNA level, ≤600,000 IU/mL	17/33	5/6	7/17	5/10
	(52%)	(83%)	(41%)	(50%)
HCV–RNA level, >600,000 IU/mL	30/83	14/28	14/39	2/16
	(36%)	(50%)	(36%)	(13%)
METAVIR F0–2	44/99	17/29	20/51	7/19
	(44%)	(59%)	(39%)	(37%)
METAVIR F3–4	2/16	1/4	1/5	0/7
	(13%)	(25%)	(20%)	(0%)
Fasting glucose level, <5.6 mmol/L	34/85	14/25	14/43	6/17
	(40%)	(56%)	(33%)	(35%)
Fasting glucose level, ≥5.6 mmol/L	13/31	5/9	7/13	1/9
	(42%)	(56%)	(54%)	(11%)
BMI < 30	31/72	13/20	13/37	5/15
	(43%)	(65%)	(35%)	(33%)
BMI ≥ 30	16/44	6/14	8/19	2/11
	(36%)	(43%)	(42%)	(18%)
RBV dose, >13 mg/kg/day	29/70	11/18	13/35	5/17
	(41%)	(61%)	(37%)	(29%)
RBV dose, ≤13 mg/kg/day	18/45	8/15	8/21	2/9
	(40%)	(53%)	(38%)	(22%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	15/27	3/3	7/16	5/8
	(56%)	(100%)	(44%)	(63%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	1/5	1/2	0/1	0/2
	(20%)	(50%)	(0%)	(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	29/72	14/26	13/35	2/11
	(40%)	(54%)	(37%)	(18%)
HCV–RNA level, >600,000 IU/mL and F3–4	1/11	0/2	1/4	0/5
	(9%)	(0%)	(25%)	(0%)
On-treatment responses
RVR	15/18	8/10	5/6	2/2
	(83%)	(80%)	(83%)	(100%)
Non-RVR	32/93	11/20	16/49	5/24
	(34%)	(55%)	(33%)	(21%)
≥4-log reduction in HCV–RNA level at wk 4	13/19	7/11	6/8	*
	(68%)	(64%)	(75%)
<4-log reduction in HCV–RNA level at wk 4	34/97	12/23	15/48	7/26
	(35%)	(52%)	(31%)	(27%)
cEVR	41/54	17/23	18/24	6/7
	(76%)	(74%)	(75%)	(86%)
Partial EVR	5/20	1/6	3/9	1/5
Combination of wk 4 response + baseline factors
RVR + baseline HCV–RNA level, ≤600,000	10/11	5/5	3/4	2/2
	(91%)	(100%)	(75%)	(100%)
RVR + baseline HCV–RNA level, >600,000	5/7	3/5	2/2	*
	(71%)	(60%)	(100%)
Non-RVR + baseline HCV–RNA level, ≤ 600,000	7/22	0/1	4/13	3/8
	(32%)	(0%)	(31%)	(38%)
Non-RVR + baseline HCV–RNA level, > 600,000	25/71	11/19	12/36	2/16
	(35%)	(58%)	(33%)	(13%)
RVR + F0–2	13/16	6/8	5/6	2/2
	(81%)	(75%)	(83%)	(100%)
RVR + F3–4	1/1	1/1	*	*
	(100%)	(100%)
Non-RVR + F0–2	31/78	11/17	15/44	5/17
	(40%)	(65%)	(34%)	(29%)
Non-RVR + F3–4	1/15	0/3	1/5	0/7
	(7%)	(0%)	(20%)	(0%)
RVR + baseline HCV–RNA level, ≤ 600,000 + F0–2	8/9	3/3	3/4	2/2
	(89%)	(100%)	(75%)	(100%)
RVR + baseline HCV–RNA level, ≤ 600,000 + F3–4	1/1	1/1	*	*
	(100%)	(100%)
RVR + baseline HCV–RNA level, > 600,000 + F0–2	5/7	3/5	2/2	*
	(71%)	(60%)	(0%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	*	*	*	*
Non-RVR + baseline HCV–RNA level, ≤ 600,000 + F0–2	7/18	*	4/12	3/6
	(39%)		(33%)	(50%)
Non-RVR + baseline HCV–RNA level, ≤ 600,000 + F3–4	0/4	0/1	0/1	0/2
	(0%)	(0%)	(0%)	(0%)
Non-RVR + baseline HCV–RNA level, >600,000 + F0–2	24/60	11/17	11/32	2/11
	(40%)	(65%)	(34%)	(18%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	1/11	0/2	1/4	0/5
	(9%)	(0%)	(25%)	(0%)

Supplementary Table 5. Multivariable Logistic Regression Models for SVR

Covariates	Odds ratio	95% CI	R2	χ2	P value
Model 1
CC genotype vs non-CC	5.93	4.57–7.69	0.148	179.84	<.0001
Caucasian vs AA ethnicity	2.77	1.96–3.92	0.026	34.5	<.0001
Hispanic vs AA ethnicity	2.03	1.20–3.43
Other vs AA ethnicity	1.65	0.73–3.75
HCV–RNA level, per 1-log unit increase	0.46	0.37–0.56	0.046	56.53	<.0001
Metavir F0 vs F4	4.94	1.77–13.75	0.008	28.02	<.0001
Metavir F1 vs F4	3.78	2.16–6.64
Metavir F2 vs F4	3.09	1.67–5.72
Metavir F3 vs F4	1.73	0.80–3.73
Fasting blood sugar level, per 1-unit decrease	1.30	1.12–1.51	0.004	11.51	.0007
BMI, per 5-unit increase	1.20	1.03–1.40	0.004	5.36	.0206
RBV, per 1-unit increase	1.10	1.01–1.20	0.003	4.54	.0332
Model 2
RVR vs (non-RVR + non-CC)	8.45	5.44–13.12	0.182	200.93	<.0001
(Non-RVR + CC) vs (non-RVR + non-CC)	6.01	4.45–8.13
Caucasian vs AA ethnicity	2.26	1.57–3.27	0.016	20.37	.0001
Hispanic vs AA ethnicity	1.82	1.05–3.14
Other vs AA ethnicity	1.31	0.57–3.00
HCV–RNA level, per 1-log unit increase until 7.0	0.55	0.44–0.69	0.02	25.96	<.0001
Metavir F0 vs F4	4.70	1.61–13.67	0.021	25.32	.0001
Metavir F1 vs F4	3.83	2.12–6.93
Metavir F2 vs F4	2.95	1.53–5.68
Metavir F3 vs F4	1.79	0.78–4.12
Fasting blood sugar level, per 1-unit decrease	1.33	1.13–0.89	0.009	11.4	.0005

NOTE. Model 1: the baseline model included IL-28B type (CC vs non-CC) and the following covariates, previously identified to be associated independently with SVR in the IDEAL study population: ethnic background, age (continuous data), sex, BMI (continuous data), baseline HCV–RNA level (continuous data, log₁₀ IU/mL), ALT level (continuous data), fasting glucose level (continuous data), hepatic steatosis (grade 0/1/2/3/4), hepatic fibrosis stage (METAVIR F0/F1/F2/F3/F4), and RBV dose (continuous data). PegIFN type was not associated with SVR in univariable analysis (Supplementary Table 11). Variables not present in the final model were removed by backward selection. A significance level of 0.05 was used for removal from the model.

Model 2: the week-4 model collapsed week-4 response and IL-28B polymorphism as a 3-level variable: (RVR vs non-RVR + CC IL-28B-type vs non-RVR + non-CC IL-28B type). Otherwise, the same covariates were included as for the baseline model.

Supplementary Table 6. Baseline Characteristics of the Adherent Subset

Baseline characteristics	Caucasians	African Americans	Hispanics	P valuea	P valueb	P valuec
N	871	191	75
Age, >40 y	755(87%)	182(95%)	53(71%)	.0008	.0002	<.0001
Male sex	542(62%)	120(62%)	46(61%)	.8769	.8783	.8209
BMI, ≥30 kg/m2	250(29%)	87(46%)	31(41%)	<.0001	.0216	.5334
HCV–RNA level, >600,000 IU/mL	727(83%)	159(83%)	54(72%)	.9406	.012	.0388
ALT level, >ULN	732(84%)	148(78%)	66(88%)	.0295	.3652	.0517
Fasting glucose level, ≥5.6 mmol/L	245(28%)	75(39%)	16(21%)	.0024	.2065	.0055
Steatosisd	517(59%)	127(67%)	51(68%)	.0676	.1426	.8141
METAVIR F3–4	101(12%)	17(9%)	12(16%)	.2831	.2591	.0946
Peginterferon-alfa
2b 1.0 ug/kg/wk	289(33%)	59(31%)	23(31%)	.3175	.8154	.4771
2b 1.5 ug/kg/wk	310(36%)	79(41%)	26(35%)
2a 180 ug/wk	272(31%)	53(28%)	26(35%)
RBV, >13 mg/kg	475(55%)	70(37%)	49(65%)	<.0001	.071	<.0001
rs12979860 Genotype frequency
CC	336(39%)	30(16%)	26(34%)	<.0001	.2091	.0006
CT	433(49%)	91(47%)	35(47%)
TT	102(12%)	70(37%)	14(19%)

Supplementary Table 7. HCV–RNA Levels at Baseline and During Treatment in the Adherent Subset

Baseline viral load, log10 IU/mL	CC	CT	TT	P valuea
				CC vs CT	CC vs TT	CT vs TT
Caucasians
N	336	433	102
Median (25th–75th percentile)	6.6(6.1–6.9)	6.4(6.0–6.7)	6.3(5.9–6.6)	<.0001	<.0001	.0117
HCV–RNA level, >600,000 IU/mL, N (%)	280/336(83.3%)	368/433(85.0%)	79/102(77.5%)	.5318	.176	.0647
African Americans
N	30	91	70
Median (25th–75th percentile)	6.6(6.2–6.9)	6.4(6.0–6.7)	6.1(5.8–6.5)	.0295	.0003	.0140
HCV–RNA level, >600,000 IU/mL, N (%)	28/30(93.3%)	77/91(84.6%)	54/70(77.1%)	.3522	.0858	.2274
Hispanics
N	26	35	14
Median (25th–75th percentile)	6.5(6.2–7.0)	6.1(5.6–6.6)	6.0(5.3–6.3)	.0243	.0245	.4621
HCV–RNA level, >600,000 IU/mL, N (%)	22/26(84.6%)	23/53(65.7%)	9/14(64.3%)	.1423	.2338	1.000

Supplementary Table 8. Median On-Treatment Reduction of HCV–RNA Levels in the Adherent Subset

Median on-treatment viral load reduction, log10 IU/mL	CC	CT	TT	P valuea
				CC vs CT	CC vs TT	CT vs TT
Caucasians
Week 2(n = 826), median (25th–75th percentile)	2.5(1.9–3.3)	0.9(0.4–1.5)	0.6(0.3–1.1)	<.0001	<.0001	.0031
Week 4(n = 832), median (25th–75th percentile)	3.7(3.0–4.7)	1.5(0.9–2.5)	1.0(0.7–2.0)	<.0001	<.0001	.0035
Week 12(n = 865), median (25th–75th percentile)	5.5(4.8–5.9)	3.7(1.7–5.0)	3.2(1.7–6.6)	<.0001	<.0001	.1005
African Americans
Week 2(n = 157), median (25th–75th percentile)	1.7(0.5–2.3)	0.7(0.4–1.1)	0.5(0.3–0.8)	.0014	.0002	.0999
Week 4(n = 162), median (25th–75th percentile)	2.7(1.1–3.6)	1.1(0.6–2.0)	0.9(0.5–1.5)	.0013	.0003	.1615
Week 12(n = 190), median (25th–75th percentile)	4.7(2.3–5.4)	1.7(1.0–4.0)	1.8(0.9–4.0)	.0001	.0003	.9521
Hispanics
Week 2(n = 74), median (25th–75th percentile)	2.3(1.6–3.7)	0.8(0.4–1.3)	0.4(0.1–1.1)	<.0001	.0002	.1629
Week 4(n = 75), median (25th–75th percentile)	3.5(2.7–4.8)	1.3(0.7–2.4)	0.7(0.4–1.8)	<.0001	.0001	.1012
Week 12(n = 74), median (25th–75th percentile)	5.4(4.8–5.9)	3.6(1.1–4.9)	1.3(0.6–3.3)	<.0001	<.0001	.0398

Supplementary Table 9. Rates of Virologic Response for Caucasian, African American, and Hispanic Populations in the Adherent Subset

	Overall	CC	CT	TT	P value
					CC vs CT	CC vs TT	CT vs TT
Rates of on-treatment response, SVR
Caucasians
SVR	488/871	274/336	180/433	34/102	<.0001	<.0001	.1266
	(56%)	(82%)	(42%)	(33%)
URVR/wk 2	49/826	40/321	7/409	2/96	<.0001	.0030	.6824
	(6%)	(12%)	(2%)	(2%)
RVR/wk 4	117/833	91/321	20/413	6/99	<.0001	<.0001	.6201
	(14%)	(28%)	(5%)	(6%)
cEVR/wk 12	500/865	295/334	173/431	32/100	<.0001	<.0001	.132
	(58%)	(88%)	(40%)	(32%)
EOTR/wk 48	604/846	310/331	241/418	53/97	<.0001	<.0001	.5887
	(71%)	(94%)	(58%)	(55%)
Relapse	116/604	36/310	61/241	19/53	<.0001	<.0001	.1186
	(19%)	(12%)	(25%)	(36%)
African Americans
SVR	45/191	16/30	17/91	12/70	.0002	.0002	.8012
	(24%)	(53%)	(19%)	(17%)
URVR/wk 2	3/157	2/25	0/77	1/55	.0582	.2288	.4167
	(2%)	(8%)	(0%)	(2%)
RVR/wk 4	7/162	3/25	3/81	1/56	.1186	.085	.6447
	(4%)	(12%)	(4%)	(2%)
cEVR/wk 12	48/190	14/30	18/90	16/70	.0042	.0173	.6612
	(25%)	(47%)	(20%)	(23%)
EOTR/wk 48	63/186	21/30	23/86	19/70	<.0001	<.0001	.9555
	(34%)	(70%)	(27%)	(27%)
Relapse	18/63	5/21	6/23	7/19	.8617	.3691	.453
	(29%)	(24%)	(26%)	(37%)
Hispanics
SVR	38/75	20/26	15/35	3/14	.0078	.0007	.0160
	(51%)	(77%)	(43%)	(21%)
URVR/wk 2	10/74	6/26	3/34	1/14	.1574	.387	1.000
	(14%)	(23%)	(9%)	(7%)
RVR/wk 4	13/75	10/26	2/35	1/14	.0015	.0344	.8505
	(17%)	(38%)	(6%)	(7%)
cEVR/wk 12	40/74	22/25	15/35	3/14	.0004	<.0001	.2024
	(54%)	(88%)	(43%)	(21%)
EOTR/wk 48	47/73	25/26	19/34	3/13	.0005	<.0001	.0438
	(64%)	(96%)	(88%)	(38%)
Relapse	9/47	5/25	4/19	0/3	.9317	.3927	.3796
	(19%)	(20%)	(21%)	(0%)
Rates of SVR by wk 4, wk 12 responses
Caucasians
RVR	112/117	87/91	19/20	6/6	.9061	.5999	.5765
	(96%)	(96%)	(95%)	(100%)
Non-RVR	355/716	177/230	152/393	26/93	<.0001	<.0001	.0537
	(50%)	(77%)	(39%)	(28%)
cEVR	435/500	264/295	146/173	25/32	.1061	.0762	.3812
	(87%)	(89%)	(84%)	(78%)
Partial EVR	50/184	8/27	34/124	8/33	.8163	.6387	.7141
	(27%)	(30%)	(27%)	(24%)
African Americans
RVR	7/7	3/3	3/3	1/1	1.000	1.000	1.000
	(100%)	(100%)	(100%)	(100%)
Non-RVR	35/155	10/22	14/78	11/55	.0076	.0235	.7656
	(23%)	(45%)	(18%)	(20%)
cEVR	37/48	13/14	13/18	11/16	.1379	.0996	.8245
	(77%)	(93%)	(72%)	(69%)
Partial EVR	7/45	3/9	3/20	1/16	.2595	.0762	.4065
	(16%)	(33%)	(15%)	(6%)
Hispanics
RVR	12/13	9/10	2/2	1/1	.6404	.7401	1.000
	(92%)	(90%)	(100%)	(100%)
Non-RVR	26/62	11/16	13/33	2/13	.0539	.0041	.7656
	(42%)	(69%)	(39%)	(15%)
cEVR	34/40	19/22	12/15	3/3	.6696	1.000	1.000
	(85%)	(86%)	(80%)	(100%)
Partial EVR	3/9	0/3	3/5	0/1	.1964	1.000	1.000
	(33%)	(0%)	(60%)	(0%)

NOTE. Data for SVR include the entire adherent subset. Data for on-treatment virologic milestones/relapse rates refer to the number of patients who had the evaluation performed. The trial protocol included a stopping rule for patients who did not attain EVR at week 12 (no EVR = reduction of serum HCV RNA < 2 log₁₀ IU at week 12).

EOTR, end-of-treatment response at week 48; URVR, ultrarapid virologic response at week 2.

Supplementary Table 10. SVR Rates for Each Genotype of the IL-28B Polymorphism in the Adherent Subset, According to Baseline Characteristics and Week 4 and Week 12 On-Treatment Responses

	Overall	CC	CT	TT
Caucasians
Overall	488/871	274/336	180/433	34/102
	(56%)	(82%)	(42%)	(33%)
Baseline factors
Age ≤ 40 y	82/116	38/45	37/58	7/13
	(71%)	(84%)	(64%)	(54%)
Age > 40 y	406/755	236/291	143/375	27/89
	(54%)	(81%)	(38%)	(30%)
Female	189/329	91/107	83/180	15/42
	(57%)	(85%)	(46%)	(36%)
Male	299/542	183/229	97/253	19/60
	(55%)	(80%)	(38%)	(32%)
HCV–RNA level, ≤600,000 IU/mL	113/144	51/56	48/65	14/23
	(78%)	(91%)	(74%)	(61%)
HCV–RNA level, >600,000 IU/mL	375/727	223/280	132/368	20/79
	(52%)	(80%)	(36%)	(25%)
METAVIR F0–2	452/770	254/296	166/384	32/90
	(59%)	(86%)	(43%)	(36%)
METAVIR F3–4	36/101	20/40	14/49	2/12
	(36%)	(50%)	(29%)	(17%)
Fasting glucose level, <5.6 mmol/L	381/626	210/247	145/301	26/78
	(61%)	(85%)	(48%)	(33%)
Fasting glucose level, ≥5.6 mmol/L	107/245	64/89	35/132	8/24
	(44%)	(72%)	(27%)	(33%)
BMI < 30	142/250	87/101	45/123	10/26
	(57%)	(86%)	(37%)	(38%)
BMI ≥ 30	346/621	187/235	135/310	24/76
	(56%)	(80%)	(44%)	(32%)
RBV dose, >13 mg/kg/day	282/475	147/176	111/238	24/61
	(59%)	(84%)	(47%)	(39%)
RBV dose, ≤13 mg/kg/day	206/396	127/160	69/195	10/41
	(52%)	(79%)	(35%)	(24%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	106/129	46/48	46/59	14/22
	(82%)	(96%)	(78%)	(64%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	7/15	5/8	2/6	0/1
	(47%)	(63%)	(33%)	(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	346/641	208/248	120/325	18/68
	(54%)	(84%)	(37%)	(26%)
HCV–RNA level, >600,000 IU/mL and F3–4	29/86	15/32	12/43	2/11
	(34%)	(47%)	(28%)	(18%)
On-treatment responses
RVR	112/117	87/91	19/20	6/6
	(96%)	(96%)	(95%)	(100%)
Non-RVR	355/716	177/230	152/393	26/93
	(50%)	(77%)	(39%)	(28%)
≥4-log reduction in HCV RNA at wk 4	157/167	125/134	28/28	4/5
	(94%)	(93%)	(100%)	(80%)
<4-log reduction in HCV RNA at wk 4	331/704	149/202	152/405	30/97
	(47%)	(74%)	(38%)	(31%)
cEVR	435/500	264/295	146/173	25/32
	(87%)	(89%)	(84%)	(78%)
Partial EVR	50/184	8/27	34/124	8/33
Combination of wk 4 response + baseline factors
RVR + baseline HCV–RNA level, ≤ 600,000	59/60	42/42	12/13	5/5
	(98%)	(100%)	(92%)	(100%)
RVR + baseline HCV–RNA level, >600,000	53/57	45/49	7/7	1/1
	(93%)	(92%)	(100%)	(100%)
Non-RVR + baseline HCV–RNA level, ≤600,000	48/71	7/10	34/45	7/16
	(68%)	(70%)	(76%)	(44%)
Non-RVR + baseline HCV–RNA level, >600,000	307/645	170/220	118/348	19/77
	(48%)	(77%)	(34%)	(25%)
RVR + F0–2	105/109	80/83	19/20	6/6
	(96%)	(96%)	(95%)	(100%)
RVR + F3–4	7/8	7/8	*	*
	(88%)	(88%)
Non-RVR + F0–2	331/637	166/204	141/352	24/81
	(52%)	(81%)	(40%)	(30%)
Non-RVR + F3–4	24/79	11/26	11/41	2/12
	(30%)	(42%)	(27%)	(17%)
RVR + baseline HCV–RNA level, ≤600,000 + F0–2	55/56	38/38	12/13	5/5
	(98%)	(100%)	(92%)	(100%)
RVR + baseline HCV–RNA level, ≤600,000 + F3–4	4/4	4/4	*	*
	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F0–2	50/53	42/45	7/7	1/1
	(94%)	(93%)	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	3/4	3/4	*	*
	(75%)	(75%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F0–2	45/64	6/7	32/42	7/15
	(70%)	(86%)	(76%)	(47%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F3–4	3/7	1/3	2/3	0/1
	(43%)	(33%)	(66%)	(0%)
Non-RVR + baseline HCV–RNA level, >600,000 + F0–2	286/573	160/197	109/310	17/66
	(50%)	(81%)	(35%)	(26%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	21/72	10/23	9/38	2/11
	(29%)	(43%)	(24%)	(18%)
African Americans
Overall	45/191	16/30	17/91	12/70
	(24%)	(53%)	(19%)	(17%)
Baseline factors
Age ≤ 40 y	3/9	0/1	2/5	1/3
	(33%)	(0%)	(40%)	(33%)
Age > 40 y	42/182	16/29	15/86	11/67
	(23%)	(55%)	(17%)	(16%)
Female	20/71	7/11	7/29	6/31
	(28%)	(64%)	(24%)	(19%)
Male	25/120	9/19	10/62	6/39
	(21%)	(47%)	(16%)	(15%)
HCV–RNA level, ≤600,000 IU/mL	14/32	2/2	6/14	6/16
	(44%)	(100%)	(43%)	(38%)
HCV–RNA level, >600,000 IU/mL	31/159	14/28	11/77	6/54
	(20%)	(50%)	(14%)	(11%)
METAVIR F0–2	42/174	15/28	16/83	11/63
	(24%)	(54%)	(19%)	(17%)
METAVIR F3–4	3/17	1/2	1/8	1/7
	(18%)	(50%)	(13%)	(14%)
Fasting glucose level, < 5.6 mmol/L	32/116	11/19	12/57	9/40
	(28%)	(58%)	(21%)	(23%)
Fasting glucose level, ≥ 5.6 mmol/L	13/75	5/11	5/34	3/30
	(17%)	(45%)	(15%)	(10%)
BMI < 30	21/104	6/14	9/51	6/39
	(20%)	(43%)	(18%)	(15%)
BMI ≥ 30	24/87	10/16	8/40	6/31
	(28%)	(63%)	(20%)	(19%)
RBV dose, >13 mg/kg/day	16/70	5/10	5/29	6/31
	(23%)	(50%)	(17%)	(19%)
RBV dose, ≤13 mg/kg/day	29/121	11/20	12/62	6/39
	(24%)	(55%)	(19%)	(15%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	14/30	2/2	6/12	6/16
	(47%)	(100%)	(50%)	(38%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	0/2	*	0/2	*
	(0%)		(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	28/144	13/26	10/71	5/47
	(19%)	(50%)	(14%)	(11%)
HCV–RNA level, >600,000 IU/mL and F3–4	3/15	1/2	1/6	1/7
	(20%)	(50%)	(17%)	(14%)
On-treatment responses
RVR	7/7	3/3	3/3	1/1
	(100%)	(100%)	(100%)	(100%)
Non-RVR	35/155	10/22	14/78	11/55
	(23%)	(45%)	(18%)	(20%)
≥4-log reduction in HCV RNA at wk 4	9/9	5/5	3/3	1/1
	(100%)	(100%)	(100%)	(100%)
<4-log reduction in HCV RNA at wk 4	36/182	11/25	14/88	11/69
	(20%)	(44%)	(16%)	(16%)
cEVR	37/48	13/14	13/18	11/16
	(77%)	(93%)	(72%)	(69%)
Partial EVR	7/45	3/9	3/20	1/16
	(16%)	(33%)	(15%)	(6%)
Combination of wk 4 response + baseline factors
RVR + baseline HCV–RNA level, ≤600,000	4/4(100%)	1/1(100%)	2/2(100%)	1/1(100%)
RVR + baseline HCV–RNA level, >600,000	3/3	2/2	1/1	*
	(100%)	(100%)	(100%)
Non-RVR + baseline HCV–RNA level, ≤600,000	9/19	*	4/8	5/11
	(47%)		(50%)	(45%)
Non-RVR + baseline HCV–RNA level, >600,000	26/136	10/22	10/70	6/44
	(19%)	(45%)	(14%)	(14%)
RVR + F0–2	7/7	3/3	3/3	1/1
	(100%)	(100%)	(100%)	(100%)
RVR + F3–4	*	*	*	*
Non-RVR + F0–2	33/145	10/22	13/73	10/50
	(23%)	(45%)	(18%)	(20%)
Non-RVR + F3–4	2/10	*	1/5	1/5
	(20%)		(20%)	(20%)
RVR + baseline HCV–RNA level, ≤600,000 + F0–2	4/4	1/1	2/2	1/1
	(100%)	(100%)	(100%)	(100%)
RVR + baseline HCV–RNA level, ≤600,000 + F3–4	*	*	*	*
RVR + baseline HCV–RNA level, >600,000 + F0–2	3/3	2/2	1/1	*
	(100%)	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	*	*	*	*
Non-RVR + baseline HCV–RNA level, ≤600,000 + F0–2	9/18	*	4/7	5/11
	(50%)		(57%)	(45%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F3–4	1/1	1/1	*	*
	(100%)	(100%)
Non-RVR+ baseline HCV–RNA level, >600,000 + F0–2	24/127	10/22	9/66	5/39
	(19%)	(45%)	(14%)	(13%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	2/9	*	1/4	1/5
	(22%)		(25%)	(20%)
Hispanics
Overall	38/75	20/26	15/35	3/14
	(51%)	(77%)	(43%)	(21%)
Baseline factors
Age ≤ 40 y	12/22(55%)	5/6(83%)	5/12(42%)	2/4(50%)
Age > 40 y	26/53	15/20	10/23	1/10
	(49%)	(75%)	(43%)	(10%)
Female	13/29	2/4	10/20	1/5
	(45%)	(50%)	(50%)	(20%)
Male	25/46	18/22	5/15	2/9
	(54%)	(82%)	(33%)	(22%)
HCV–RNA level, ≤600,000 IU/mL	12/21	4/4	6/12	2/5
	(57%)	(100%)	(50%)	(40%)
HCV–RNA level, >600,000 IU/mL	26/54	16/22	9/23	1/9
	(48%)	(73%)	(39%)	(11%)
METAVIR F0–2	35/63	18/22	14/31	3/10
	(56%)	(82%)	(45%)	(30%)
METAVIR F3–4	3/12	2/4	1/4	0/4
	(25%)	(50%)	(25%)	(0%)
Fasting glucose level, <5.6 mmol/L	29/59	17/21	9/28	3/10
	(49%)	(81%)	(32%)	(30%)
Fasting glucose level, ≥5.6 mmol/L	9/16	3/5	6/7	0/4
	(56%)	(60%)	(86%)	(0%)
BMI < 30	24/44	15/17	6/18	3/9
	(55%)	(88%)	(33%)	(33%)
BMI ≥ 30	14/31	5/9	9/17	0/5
	(45%)	(56%)	(53%)	(0%)
RBV dose, >13 mg/kg/day	26/49	14/18	9/22	3/9
	(53%)	(78%)	(41%)	(33%)
RBV dose, ≤13 mg/kg/day	12/26	6/8	6/13	0/5
	(46%)	(75%)	(46%)	(0%)
Combination of baseline factors
HCV–RNA level, ≤600,000 IU/mL and F0–2	10/17	2/2	6/11	2/4
	(59%)	(100%)	(55%)	(50%)
HCV–RNA level, ≤600,000 IU/mL and F3–4	2/4	2/2	0/1	0/1
	(50%)	(100%)	(0%)	(0%)
HCV–RNA level, >600,000 IU/mL and F0–2	25/46	16/20	8/20	1/6
	(54%)	(80%)	(40%)	(17%)
HCV–RNA level, >600,000 IU/mL and F3–4	1/8	0/2	1/3	0/3
	(12.5%)	(0%)	(33%)	(0%)
On-treatment responses
RVR	12/13	9/10	2/2	1/1
	(92%)	(90%)	(100%)	(100%)
Non-RVR	26/62	11/16	13/33	2/13
	(42%)	(69%)	(39%)	(15%)
≥4-log reduction in HCV RNA at wk 4	10/11	8/9	2/2	*
	(91%)	(89%)	(100%)
<4-log reduction in HCV RNA at wk 4	28/64	12/17	13/33	3/14
	(44%)	(71%)	(39%)	(21%)
cEVR	34/40	19/22	12/15	3/3
	(85%)	(86%)	(80%)	(100%)
Partial EVR	3/9	0/3	3/5	0/1
	(33%)	(0%)	(60%)	(0%)
Combination of wk 4 response + baseline factors
RVR + baseline HCV RNA ≤ 600,000	6/6(100%)	4/4(100%)	1/1(100%)	1/1(100%)
RVR + baseline HCV–RNA level, >600,000	6/7	5/6	1/1	*
	(86%)	(83%)	(100%)
Non-RVR + baseline HCV–RNA level, ≤600,000	6/15	*	5/11	1/4
	(40%)		(45%)	(25%)
Non-RVR + baseline HCV–RNA level, >600,000	20/47	11/16	8/22	1/9
	(43%)	(69%)	(36%)	(11%)
RVR + F0–2	10/11	7/8	2/2	1/1
	(91%)	(88%)	(100%)	(100%)
RVR + F3–4	2/2	2/2	*	*
	(100%)	(100%)
Non-RVR + F0–2	25/52	11/14	12/29	2/9
	(48%)	(79%)	(41%)	(22%)
Non-RVR + F3–4	1/10	0/2	1/4	0/4
	(10%)	(0%)	(25%)	(0%)
RVR + baseline HCV–RNA, ≤600,000 + F0–2	4/4	2/2	1/1	1/1
	(100%)	(100%)	(100%)	(100%)
RVR + baseline HCV–RNA level, ≤600,000 + F3–4	2/2	2/2	*	*
	(100%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F0–2	6/7	5/6	1/1	*
	(86%)	(83%)	(100%)
RVR + baseline HCV–RNA level, >600,000 + F3–4	*	*	*	*
Non-RVR + baseline HCV–RNA level, ≤60,0000 + F0–2	6/13	*	5/10	1/3
	(46%)		(50%)	(33%)
Non-RVR + baseline HCV–RNA level, ≤600,000 + F3–4	0/2	*	0/1	0/1
	(0%)		(0%)	(0%)
Non-RVR + baseline HCV–RNA level, >600,000 + F0–2	19/39	11/14	7/19	1/6
	(49%)	(79%)	(37%)	(17%)
Non-RVR + baseline HCV–RNA level, >600,000 + F3–4	1/8	0/2	1/3	0/2
	(13%)	(0%)	(33%)	(0%)

Supplementary Table 11. SVR Rates for Each Genotype of the IL-28B Polymorphism in the Overall Cohort, According to PegIFN Type

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• Supplementary Figure 1. 

  Median reductions in viral load from baseline on the basis of IL-28B genotype in the adherent subset. (A) Caucasians, (B) African Americans, and (C) Hispanics. Bars represent 25th and 75th percentiles. Statistical comparisons are presented in Supplementary Table 7, Supplementary Table 8.

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• Supplementary Figure 2. 

  Virologic responses on treatment on the basis of IL-28B SNP genotype and ethnicity in the adherent subset. (A) Caucasians, (B) African Americans, and (C) Hispanics. EOTR, end-of-treatment response. Statistical comparisons are presented in Supplementary Table 7, Supplementary Table 8.

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