Antiviral activity of TMC435 monotherapy in patients infected with HCV genotypes 2-6: TMC435-C202, a phase IIa, open-label study
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Journal of Hepatology
"In spite of study limitations outlined above, the results of this phase IIa study in 37 treatment-naïve patients suggest that this investigational agent may be a future candidate for treatment of infection with HCV genotypes 4, 5, and 6, and potentially with particular subtypes of genotype 2."
Background & Aims
TMC435 is an investigational, once-daily, oral NS3/4A protease inhibitor currently in phase III development for the treatment of hepatitis C virus (HCV) infection. Phase I and II studies in patients infected with HCV genotype 1 have demonstrated that TMC435 is generally well tolerated, has a pharmacokinetic profile that supports once daily dosing, and demonstrates potent antiviral activity. This phase IIa study (TMC435-C202; NCT00812331) was conducted to investigate the antiviral activity, safety, tolerability, and pharmacokinetics of TMC435 in treatment-naïve patients infected with HCV genotypes 2-6.
The study consisted of 7days of monotherapy with TMC435 (200mg once daily). Patients could begin treatment with pegylated interferon/ribavirin from day 8 with a follow-up period up to days 37-42.
Thirty-seven patients were enrolled in Germany, Belgium and Thailand. For the primary end point at day 8, the mean (± standard error) change in plasma HCV ribonucleic acid (log10IU/ml) from baseline was the greatest for genotypes 6 (-4.35±0.29) and 4 (-3.52±0.43), followed by genotypes 2 (-2.73±0.71) and 5 (-2.19±0.39). No antiviral activity was evident for genotype 3. Viral breakthrough occurred in six patients during the monotherapy phase and in six additional patients during PegIFN/RBV-only period. All adverse events were mild or moderate and there were no discontinuations during the TMC435 monotherapy period.
The results of this phase IIa proof-of-concept trial provide evidence that TMC435 has a spectrum of activity against multiple HCV genotypes, except for genotype 3. In this study, TMC435 was generally safe and well tolerated.
The hepatitis C virus (HCV) is a single-stranded RNA virus and one of the leading causes of chronic liver disease worldwide . It is estimated that 130-170million people are infected with HCV, constituting 2.2-3.0% of the global population .
HCV can be classified into six major genotypes based on sequence divergence of 30% . Genotype 1 has a broad global distribution , , , , , , . Genotype 2 is prevalent in North America, Europe, and Japan (subtypes 2a and 2b), Northern Italy (2c) , and Western Africa . Genotype 3 is known for its wide distribution among intravenous drug users in a number of countries , , , and is also predominant in India and Pakistan . Genotype 4 is responsible for >90% of HCV infections in Egypt, where it is associated with the re-use of needles during mass administration of parenteral antischistosomal therapy until the 1980s, and is also prevalent in other regions of the Middle East and sub-Saharan Africa , , , . In Europe, its prevalence has recently increased due to immigration and transmission between intravenous drug users . Genotype 5 is found most commonly in South Africa, as well as in four regions in France, Spain, Syria, and Belgium , . Genotype 6 is found in South East Asia and surrounding regions where overall HCV prevalence is high , , .
The recommended treatment for patients infected with non-genotype 1 HCV is pegylated interferon and ribavirin (PegIFN/RBV). Treatment for different genotypes differs slightly, with PegIFN alpha (α) plus weight-based RBV for 48weeks recommended for genotypes 1, 4, and 6, and PegIFNα plus low-dose RBV (800mg) for 24weeks for genotypes 2 and 3 , , , , , . Of note, given the recent approval of the HCV NS3/4A protease inhibitors boceprevir and telaprevir , , the standard of care for genotype 1 is expected to change , .
Sustained virologic response (SVR, undetectable HCV RNA in patients' plasma 24weeks after end of treatment) is achieved in approximately 75% of patients infected with genotypes 2 and 3 . Rates with genotypes 4, 5, or 6 are 43-70% . Furthermore, PegIFN/RBV therapy is poorly tolerated in some patients. In randomised trials of PegIFNα/RBV, influenza-like and neuropsychiatric symptoms occurred in up to 24-64% of patients , , adverse events (AEs) led to study discontinuation in 14-32% and dose reduction in 11-42% , , and anaemia or neutropenia led to dose reduction in 9-22% and 18-20%, respectively , .
It is, therefore, clear that novel direct-acting antivirals (DAAs) are required to address issues of sub-optimal efficacy, poor tolerability and compliance failures, and to reduce treatment duration. Boceprevir and telaprevir have demonstrated significantly improved virologic outcomes in both treatment-naïve and -experienced genotype 1 patients , . However, their thrice daily dosing schedule (with food) and increased rates of AEs including anaemia and rash, in comparison to PegIFN/RBV, suggest that there is still room for improvement. Furthermore, activity in other genotypes has not been extensively investigated.
TMC435 is an investigational, once-daily oral NS3/4A protease inhibitor currently in phase III clinical development for the treatment of HCV infection. Phase I and II trials in patients infected with HCV genotype 1 have demonstrated that TMC435 is generally well tolerated, has a pharmacokinetic profile that supports once daily (q.d.) dosing, and demonstrates potent antiviral activity and efficacy , , , .
Given sub-optimal responses to existing treatment options and the worldwide distribution of genotype 1, this genotype is the current focus of the TMC435 clinical development programme. A phase IIa study (TMC435-C202; NCT00812331) was also performed in patients infected with genotypes 2-6 to assess the antiviral activity of TMC435 against these genotypes. Data from biochemical protease assays available before the study start indicated that TMC435 is a potent NS3/4A protease inhibitor in genotypes 2, 4, 5, and 6, with a medium inhibitory concentration (IC50) of <13nM for all HCV NS3/4A enzymes tested . IC50 for genotype 3 was 37nM . This study assessed antiviral activity, safety, tolerability, and pharmacokinetics of TMC435 (200mgq.d. administered for 7days as monotherapy) in treatment-naïve patients infected with HCV genotypes 2-6.
The results of this phase IIa proof-of-concept trial provide evidence that TMC435 has a broad spectrum of activity against multiple HCV genotypes, with the exception of genotype 3.
Monotherapy with oral TMC435 200mgq.d. for 7days was associated with potent antiviral activity in patients infected with genotypes 2, 4, 5, and 6. The greatest antiviral activity was observed among patients infected with genotypes 4 and 6, followed by genotypes 2 and 5. Of note, potent activity was observed in three patients with genotype 2, with limited activity observed in the other three patients in this cohort. No antiviral activity was seen against genotype 3. Viral breakthrough (protocol defined: plasma HCV RNA increase >1log10IU/ml from the lowest reached, or >100IU/ml in patients whose HCV RNA was previously <25IU/ml undetectable or detectable) occurred in six patients during the monotherapy phase. Six additional patients had viral breakthrough during the PegIFN/RBV-only period, and could therefore be considered viral rebound after cessation of treatment with TMC435. In this study, TMC435 was generally safe and well tolerated. All AEs were mild to moderate and during the 7-day period of TMC435 monotherapy there were no discontinuations or untoward changes in biochemical parameters.
This is the first study in which an HCV protease inhibitor has demonstrated antiviral activity in genotypes 5 and 6. Furthermore, data for genotypes 2, 3, and 4 are limited for other investigational agents. In a phase IIa study, telaprevir combined with PegIFN/RBV showed substantial activity against genotype 2, modest activity against genotype 4 , and limited activity against genotype 3 . Of note, unlike nucleotide inhibitors, NS3 protease inhibitors are generally considered to have limited activity in certain genotypes. However, the results of this study suggest that the protease inhibitor TMC435 could be efficacious across multiple genotypes, though additional clinical data are required to provide further support.
A limitation of this study relates to the high subtype diversity in genotypes 2, 4, and 6 (such diversity is not observed in genotypes 3 and 5). Not all subtypes were included in this study and the number of patients per subtype was sometimes limited. Importantly, no difference in efficacy between included subtypes was observed in genotypes 4 or 6. The difference in antiviral activity between patients infected with genotype 2 may be caused by the different subtypes, as HCV RNA change from baseline at day 3 in patients infected with 2b and 2c was -3.19 to -3.61log10IU/ml, compared with -0.26 to -0.99 in those infected with 2, 2k, and 2i. In addition to this limitation, the sample size in each cohort was relatively small. It should also be noted that a TMC435 dose of 200mgq.d. was administered in this trial, whereas a dose of 150mg is currently in phase III development.
The lack of antiviral activity against genotype 3, compared with other genotypes, is consistent with the lower IC50 value of TMC435 against a genotype 3 isolate in an in vitro biochemical assay . It is suggested that this may be due to the presence of a naturally occurring D168Q polymorphism at baseline, which is present in most genotype 3a isolates known to date and was observed in all genotype 3a patients included in this study (data not shown). A D168Q mutation alone has been shown to reduce TMC435 activity in a genotype 1b replicon assay by >700-fold . TMC435 exposure (as indicated by C0h, Cmin, Cmax, and AUC24h) was lower in genotypes 2 and 3 than in genotypes 4, 5, and 6, though it is suggested that this may be due to chance due to the small number of patients in this study. Furthermore, as mean AUC values were <3-fold lower in the genotype 3 cohort compared to genotype 6 but in vitro susceptibility of genotype 3 isolates was >700-fold lower, the lower exposure observed in this cohort does not explain the lack of antiviral activity against genotype 3.
In patients infected with HCV genotype 4, mean change from baseline in HCV RNA began to increase after day 5. Prior to day 8, this was driven by two patients who experienced viral breakthrough under TMC435 monotherapy. The further increase in HCV RNA after day 8 is thought to reflect a lack of response to PegIFN/RBV.
Novel agents for the treatment of genotypes 4-6 would be advantageous as SVR rates are low , , and together with genotype 1 these groups are considered 'difficult to treat'. Antiviral activity against genotypes 4-6 observed in this study suggests that TMC435 could provide a clinical benefit, particularly for patients infected with genotypes 4 and 6. For genotype 5, the mean decline in HCV RNA from baseline over the 7-day monotherapy period was slightly lower compared to genotypes 4 and 6, suggesting that the TMC435 activity was somewhat lower in this group. Due to SVR rates of 70% in genotype 2 and 3 patients following treatment with PegIFN/RBV, there is perhaps a less urgent need for novel agents to treat infection with these genotypes, though patients who do not respond to treatment could benefit from regimens including novel DAAs. TMC435 showed antiviral activity in three/six patients infected with genotype 2, and no activity against genotype 3.
Of note, given the high sequence variability between the different genotypes and subtypes, further work is ongoing to investigate the role of naturally occurring baseline polymorphisms in variation of the virologic response, and to fully characterise viral variants observed in patients with viral breakthrough.
In spite of study limitations outlined above, the results of this phase IIa study in 37 treatment-naïve patients suggest that this investigational agent may be a future candidate for treatment of infection with HCV genotypes 4, 5, and 6, and potentially with particular subtypes of genotype 2.
Patient demographics and baseline characteristics
The trial was conducted from March 3 to November 18, 2009. A total of 37 patients were enrolled (Fig. 1) across Germany, Belgium, and Thailand. No major differences in demographics and baseline disease characteristics were observed, except that all patients with genotype 6 were Asian, and median age of patients with genotype 5 was higher compared with other genotype cohorts (Supplementary Table 1). Overall, 11% of patients in the study had cirrhosis (Metavir score F4), including patients infected with genotype 2 (n=1), genotype 3 (n=1), and genotype 5 (n=2). Multiple subtypes were included in cohorts for genotype 2 (2b, 2c, 2i, 2k), genotype 4 (4, 4c, 4d), and genotype 6 (6a, 6c-l, 6j, 6n) (Fig. 2).
Following the 7-day TMC435 treatment period, all patients started PegIFN/RBV therapy. Thirty-one patients began PegIFN/RBV on day 8 or 9, whereas one patient with genotype 3 and five with genotype 6 began PegIFN/RBV after day 9.
Change in plasma HCV RNA from baseline
An initial rapid decline in HCV RNA from baseline at day 3 of TMC435 monotherapy was evident for all patients infected with HCV genotypes 4-6, and for three out of six patients with genotype 2 (Fig. 3, Fig. 4). Of these three patients, those who responded were infected with subtypes 2b and 2c.
At day 3, the mean (± standard error [SE]) change from baseline in plasma HCV RNA (log10IU/ml) was greater for genotypes 6 (-3.57±0.197) and 4 (-3.43±0.167), followed by genotypes 5 (2.71±0.335) and 2 (-2.02±0.625). For the primary end point at day 8, the mean (± SE) change from baseline was greater for genotypes 6 (-4.35±0.29) and 4 (-3.52±0.43) cohorts, followed by genotypes 2 (-2.73±0.71) and 5 (-2.19±0.39) (Fig. 3). However, no clear antiviral activity was evident for patients with genotype 3 (change from baseline at day 3 and 8; Fig. 3, Fig. 4). At day 8, four patients (two patients with genotype 4 and two with genotype 6) achieved HCV RNA levels of <25IU/ml detectable. No patients achieved HCV RNA levels of <25IU/ml undetectable at day 8.
From day 8 to the end of follow-up 2 (days 37-42), when patients had been treated with PegIFN/RBV only for up to 35days, mean HCV RNA declined in all genotypes, with the exception of genotype 4 where mean HCV RNA began to increase (Fig. 3). By the end of follow-up 2, HCV RNA change from baseline was -5.19±0.37 for genotype 2, -4.96±0.37 for genotype 3, -3.26±0.77 for genotype 4, -3.89±0.60 for genotype 5, and -5.46±0.32 for genotype 6. HCV RNA was <25IU/ml detectable for 5/6 (83%), 6/8 (75%), 5/8 (63%), 2/7 (29%), and 7/8 (88%) patients with genotypes 2, 3, 4, 5, and 6, respectively. HCV RNA <25IU/ml undetectable was achieved by 5/6 (83%), 3/8 (38%), 5/8 (63%), 1/7 (14%), and 6/8 (75%) patients with genotypes 2, 3, 4, 5, and 6, respectively.
One patient infected with genotype 3, two with genotype 4 and three with genotype 5 experienced viral breakthrough during the TMC435 monotherapy period. In addition, six patients experienced viral breakthrough during the follow-up period, whilst being treated with PegIFN/RBV only, suggesting lack of activity of PegIFN/RBV treatment in these patients: two infected with genotype 2, one with genotype 3, one with genotype 4, and two with genotype 6.
In genotype 2 and 3-infected patients with viral breakthrough, viral sequencing did not reveal emerging mutations. However, for most genotype 4, 5, and 6 patients with viral breakthrough, emerging mutations were detected. The most frequently observed emerging mutations in the NS3 protease domain were R155K, D168E, and D168V (data not shown).
Safety and tolerability
The type and incidence of AEs (all Grade 1-2) during the 7-day TMC435 monotherapy period was similar across all cohorts in the study (Table 1) and the most common AEs were influenza-like illness and headache. There were no clinically relevant changes in laboratory parameters, and no clinically significant findings in terms of vital signs, physical examinations, or ECG recordings. Mild elevations in bilirubin (total, direct, and indirect) levels were observed in all cohorts. Mean change from baseline to day 8 was 1.38μmol/l (95% confidence interval [CI] 0.88, 1.87) for direct and 3.06μmol/l (95% CI 1.51, 4.61) for indirect bilirubin. These returned to baseline value after completion of TMC435 dosing and were not associated with clinical symptoms or elevations in aspartate aminotransferase, alanine aminotransferase or alkaline phosphatase (Supplementary Table 2).
On day 8 (after the 7-day dosing period with TMC435 was completed), one patient experienced an serious adverse event (SAE) of Grade 1 ileitis not considered related to TMC435 therapy. The patient was discontinued from the study and recovered after 4days. No other discontinuations due to AEs occurred during the trial.
Steady state TMC435 C0h, Cmin, Cmax and AUC24h were similar for genotype 4, 5, and 6 cohorts, though lower values were observed for genotype 2 and 3 cohorts with the lowest values in the genotype 3 cohort (Supplementary Table 3). tmax values were generally similar for all genotype cohorts (Supplementary Table 3). Exposure did not differ according to race or cirrhosis (data not shown).