New treatments for HCV: Perspective from Asia.

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Introduction

The prevalence and number of people with antibodies to hepatitis C virus (anti‐HCV) globally are estimated to be 2.8% and 185 million respectively, with two‐thirds (124 million) in Asia.1

HCV genotype distribution varies greatly in the Asian regions, with estimated populations of 54, 12, 48, 7.5, and 9.7 million, respectively, for HCV genotype 1 (HCV‐1), HCV‐2, HCV‐3, HCV‐4, and HCV‐6, respectively (Table 1).2

Table 1

Estimated Prevalence of HCV Infection in Asia‐Pacific Countries

HCV Population	Asia‐Pacific Countries (million)	Global Estimation (million)	Percentage
Anti‐HCV seropositive population	> 124	184	67%
HCV genotype population
HCV genotype 1*, widely in Asia‐Pacific	54	83	65%
HCV genotype 2, East, Southeast and South Asia	12	16.5	72%
HCV genotype 3, South and Southeast Asia	48	54	88%
HCV genotype 4, Middle East	> 7.5	15	> 50%
HCV genotype 5, rare	0.1	1.5	6.7%
HCV genotype 6, Southeast Asia	9.7	9.8	99%

Asian countries included all Asia and Australia/New Zealand

Prevalence of anti‐HCV in Asian countries, data derived from Hanafiah et al.1

Distribution of HCV genotype in Asia‐Pacific countries, data derived from Messina et al.2

*More than 90% of infected individuals in East Asia are infected by HCV subtype 1b

More than 80% of Asian persons infected with HCV have a more favorable host genotype (either interleukin‐28B (IL28B) rs12979860 CC versus CT or TT or IL28B rs8099917 TT versus GT or GG). These innate immune genotypes are associated with a higher rate of sustained virological response (SVR) to treatment with pegylated interferon and ribavirin. For example, 80% of Asian HCV gentotype‐ 1 patients with lower baseline viral loads (LVL) and the IL28B CC host genotype can expect to achieve an SVR after a 24‐week course of peginterferon/ribavirin.

Peginterferon/Ribavirin for Asian Patients

For Asian patients infected by HCV genotype 1 or 4, the SVR rates in response to peginterferon/ribavirin for 48 weeks and 24 weeks are 60% and 75%, whereas for patients with genotype 2 or 3 virus the rates of SVR rise to 80% and 90% respectively.5 With a strategy of response‐guided therapy (RGT) based on HCV genotype and treatment virological responses,6 treatment duration could be abbreviated to 24 weeks for HCV‐1/4 patients with a low viral load (LVL) (ie less than one million IU/mL) and rapid virological response (RVR) (undetectable HCV RNA at treatment week 4 [W4]) and to 16 weeks for HCV‐2 patients with RVR. Treatment should be stopped for those not achieving an early virological response (EVR) (HCV RNA decline < 2 logs at W12). Extending treatment to 72 weeks is recommended for HCV‐1 patients with partial EVR (HCV RNA detectable at W12 with EVR).

Among treatment‐experienced patients in Asia, the administration of peginterferon/ribavirin for 48 weeks to HCV genotype‐1 IL28B CC relapsers7 or for 24 weeks to HCV genotype‐2 relapsers8 achieved an SVR in greater than 60% of cases.

Perspective of Directly‐Acting Antiviral Agent in Asia

The progress of directly‐acting antiviral agent (DAA) in HCV treatment is moving from interferon‐containing regimens in 2011 to interferon‐free regimens, which are the current standard of care in most Western countries.9 Table 2 and Figure 1 demonstrate the timeline and expected indications of DAA regimens in Asia‐Pacific countries. Unfortunately, the variety and uncertainty of the timeline for DAAs in Asia‐Pacific make it difficult to develop a universal HCV practice guideline appropriate for the whole Asian population.

Table 2

Expected Indications of DAA Regimens in Asia‐Pacific Countries

DAA Regimen	Treatment Duration	HCV Genotype	Decompensated Liver Diseases
Interferon‐Containing Regimens
aBoceprevir + PR, RGT (Boceprevir 800 mg every 8 hr, 24–44 wk)	28–48 weeks	G1	No
aTelaprevir + PR, RGT (Telaprevir 1125 mg every 12 hr, 12 wk)	24–48 weeks	G1/2	No
aSimeprevir + PR (Simeprevir 150 mg daily, 12 wk)	24–48 weeks	G1/4	No
aSofosbuvir + PR (Sofosbuvir 400 mg daily, 12 w)	12 weeks	G1/3–6	No
aDaclatasvir + PR, RGT (Daclatasvir 60 mg daily, 24 wk)	24–48 weeks	G4	No
Interferon‐Free Regimens
aSofosbuvir + RBV	12–24 weeks	G1–6	Yes
bSofosbuvir + Simeprevir ± RBV	12 weeks	G1	No
aDaclatasvir + Asunaprevir	24 weeks	G1b	No
aDaclatasvir + Sofosbuvir ± RBV	12–24 weeks	G1–4	Yes
a Sofosbuvir + Ledipasvir ± RBV	8–24 weeks	G1/3/4	Yes
c Ritonavir ± Ombitasvir + Dasabuvir ± RBV	12–24 weeks	G1	Yes
d Daclatasvir + Asunaprevir + BMS‐791325	12 weeks	G1	No
d Grazoprevir + Elbasvir ± RBV	12 weeks	G1–6	No

DAA, directly‐acting antiviral agent; RGT, response‐guided therapy; G, genotype; P, peginterferon; R or RBV, ribavirin.

Approved regimens in the United States, European Union, or Japan.

Off‐label regimen.

Regimen awaiting approval.

Regimens of ongoing phase 3 trials.

Underlining indicates fixed‐dose combination.

Figure 1

DAA landscape in Asian countries.

AU, Australia; DAA, directly‐acting antiviral agent; HK, Hong Kong; ID, Indonesia; JP, Japan; KR, Korea; MO, Macau; MY, Malaysia; NZ, New Zealand; P, peginterferon; PH, Philippines; R, ribavirin, SG, Singapore; TH, Thailand; TW, Taiwan; VN, Vietnam; HCV, hepatitis C virus.

HCV Practice Recommendations in the transition era of DAA in Asian countries. (2a) IFN‐eligible naïve patients without DAA available; (2b) IFN‐eligible naïve patients with DAA available; (2c) IFN‐eligible experienced patients without DAA available; (2d) IFN‐eligible experienced patients with DAA available.

Abbreviations: RVR, rapid virological response, HCV RNA undetectable at week 4; EVR, early virological response, HCV RNA decline > 2 logs at week 12; cEVR, complete EVR, no RVR, but HCV RNA undetectable at week 12; HCV RNA decline > 2 logs but detectable at week 12.

BL, baseline; IL28B CC, interleukin‐28B CC genotype; PegIFN, peginterferon; RBV, ribavirin; W, treatment week; G2, HCV genotype 2; DAA, directly‐acting antiviral agent.

Interferon‐Containing Regimens

The first wave of NS3/4A protease inhibitors, boceprevir and telaprevir, in combination with peginterferon/ribavirin for between 24 and 48 weeks based on RGT, was approved for HCV‐1 treatment‐naïve and experienced patients in several Asian countries. However, adding a first generation protease inhibitor had no benefit for HCV‐1 treatment‐naïve patients with LVL and RVR compared with a 24‐week course of peginteferon and ribavirin.10 Japan approved 24‐week telaprevir triple therapy for HCV‐2 in September 2014.

Simeprevir, a second wave protease inhibitor, has recently been approved in Japan and Australia, for use in concert with peginterferon and ribavirin for HCV genotype 1 and 4 patients, both treatment‐naive and treatment experienced.

Sofosbuvir, a pangenotypic NS5B nucleotide polymerase inhibitor with high efficacy (SVR rates > 90%) has recently received approval in Australia and Macau for use in conjunction with with pegylated interferon and ribavirin for 12 week course of therapy in HCV genotypes 1, 3‐6.

Daclatasvir, a NS5A inhibitor, in combination with peginterferon/ribavirin based on RGT, was approved for HCV‐4 patients in Europe in October 2014.

Interferon‐Free Regimens

Sofosbuvir plus a weight‐based dose of ribavirin, was approved for all HCV genotypes in Australia and 2014, thereby becoming the first interferon‐free regimen approved for use in Asia. A 12‐week and 24‐week regimen is recommended for HCV‐2 and HCV‐3 patients, respectively, with SVR rates of > 90%. However, 24 weeks of sofosbuvir/ribavirin, with SVR rate of 60% to 70% for HCV‐1 patients, is an alternative recommendation for interferon‐ineligible patients.

Instead, 12 weeks for sofosbuvir plus simeprevir, with high SVR rates (> 90%) in phase 2 COSMOS trial, is an off‐label recommendation for HCV‐1/interferon‐ineligible patients.

The first approved interferon‐free regimen for HCV‐1b, 24‐week daclatasvir plus asunaprevir (NS3/4A protease inhibitor), was approved in Japan in July 2014 for interferon‐ineligible/intolerant and treatment‐experienced patients with SVR rates of 85% to 90%.

Sofosbuvir plus daclatasvir with/without ribavirin for 12 to 24 weeks was approved for naïve or experienced HCV1‐4 patients in Europe in August 2014. A fixed‐dose combination of sofosbuvir/ledipasvir, a NS5A inhibitor, for 8 to 12 weeks with SVR rates of > 92% for HCV‐1 treatment‐naïve and experienced patients was approved in the United States in October 2014. Both regimens are expected to be available in Asia before 2016.

A 3‐DAA (coformulated paritaprevir [NS3/4A protease inhibitor boosted by ritonavir]/Ombitasvir [NS5A inhibitor] and Dasabuvir [NS5B nonnucleoside analogue]) plus ribavirin for 12 weeks achieved high SVR rates (90%‐95%) for naïve and experienced, cirrhotic and noncirrhotic HCV‐1 patients in phase 3 trials.

Recently, two fixed‐dose combinations, 12‐week daclatasvir/asunaprevir/BMS‐791325 (NS5B nonnucleoside analogue) and 12‐week grazooprevir (NS3/4A protease inhibitor)/elbasvir (NS5A inhibitor) could attain SVR rates of > 90% for HCV‐1 and HCV1‐6, respectively. The phase 3 studies are ongoing now.

HCV Practice Recommendation in Asia‐Pacific

Lacking a one‐size‐fits‐all regimen increases HCV treatment complexity and barriers. The current recommendations should be based on the availability, indication, and cost‐effectiveness of DAAs in Asia (Table 2).

Treatment‐naïve interferon‐eligible patients without DAA available (Fig. 2a)

The treatment algorithm is based on the 2012 Asian Pacific Association for the Study of the Liver (APASL) HCV practice guideline6 with modification: treatment should be stopped for HCV‐1 patients with HCV RNA decline < 1 log at W4 (interferon‐nonresponsiveness)11 and for HCV‐2/3 patients without EVR.12

Treatment‐naïve interferon‐eligible patients with DAA available (Fig. 2b)

HCV‐1, 4, 6:

DAA‐containing regimens for patients with high viral load (HVL) and IL28B‐non‐CC genotype.

Either peginterferon/ribavirin dual therapy or DAA‐containing regimens for patients of LVL/IL28B‐CC without rapid virological response (RVR), LVL/IL28B‐non‐CC, or HVL/IL28‐CC, based on cost‐effectiveness.

Twenty‐four weeks of peginterferon/ribavirin for patients with LVL and IL28B‐CC genotype if only boceprevir/peginterferon/ribavirin, telaprevir/peginterferon/ribavirin, simeprevir/peginterferon/ribavirin, or daclatasvir/peginterferon/ribavirin are available.

HCV‐2/3:

Sixteen to 24 weeks of RGT with peginterferon/ribavirin for noncirrhotic patients.

DAA‐containing regimens for cirrhotic patients, and for non‐RVR patients if cost‐effective.

Treatment‐experienced interferon‐eligible patients without DAA available (Fig. 2c)

Forty‐eight weeks of peginterferon/ribavirin for HCV‐1,4,6 prior relapsers with IL28B‐CC genotype; 24 weeks of peginterferon/ribavirin for HCV‐2/3 prior relapsers.

Treatment should be stopped for patients without EVR and for HCV‐1 with HCV RNA decline < 1 log at W4.

Deferring treatment for all prior partial/null responders and for HCV‐1 IL28B‐non‐CC patients.

Treatment‐experienced interferon‐eligible patients with DAA available (Fig. 2d)

DAA‐containing regimens for all patients.

Alternatively, 48 weeks of peginterferon/ribavirin for HCV‐1,4,6 prior relapsers with IL28B‐CC genotype, and 24 weeks of peginterferon/ribavirin for HCV‐2/3 prior relapsers, if cost‐effective.

Interferon‐ineligible/intolerant patients

Interferon‐free DAA regimens according to viral genotypes.

Conclusion

In the emerging era of DAA, treatment should weigh the benefit/risk and cost‐effectiveness, especially in lower socioeconomic areas of Asia. Before the availability of interferon‐free DAA regimens, peginterferon/ribavirin will hang around years in a number of Asian countries.