Two Approvals Offer Even More Options for HCV Treatment
The approval of two new regimens for treating hepatitis C comes as a very welcome development in the field. It is great news for patients and providers because both regimens offer new options for therapy.
For patient populations that we have been accustomed to treating with high levels of efficacy and tolerability, we now have new features like shorter duration of therapy. For those who previously failed direct- acting antiviral therapy who previously had no treatment, we now have an approved regimen.
Fortunately, only a small number of our patients — under 5% — falls into the category of having failed previous DAA therapy. Yet it has been a cherished goal in the field to be able to cure every single patient and leave no patient without a cure. Vosevi (sofosbuvir/velpatasvir/voxilaprevir; SOF/VEL/VOX, Gilead Sciences) should go a long way in helping us do that.
Vosevi is a combination of voxilaprevir, a potent and pangenotypic protease inhibitor that covers the most protease inhibitor resistant variants capable of emerging after exposure to first generation members of the protease inhibitor class, with the components of an already approved product, Epclusa (sofosbuvir/velpatasvir; SOF/VEL, Gilead Sciences), a combination of the pangenotype NS5A inhibitor, velpatasvir, and the familiar nucleotide polymerase inhibitor sofosbuvir. That dual combination has had the distinction being the first approved pangenotypic regimen and it’s already in widespread use. Because of the incremental efficacy it offers in genotypes 2 and 3 compared with earlier regimens, including genotype 3 patients with cirrhosis, it represented a particular step forward for patients with genotypes 2 and 3 and has become the treatment of choice for these genotypes, as reflected in the AASLD Guidance (hcvguidelines.org) since its approval in 2016.
There have been a number of studies looking at various regimens for patients who fail first-generation DAAs. The regimens studied have sometimes consisted of a longer duration of treatment of the same regimen the patient received before or the same regimen for the same or longer duration combined with ribavirin. Less often, researchers have studied a combination of regimens made by different manufacturers combined in an individualized non-FDA approved manner. Some of these regimens such as Viekira Pak (ombitasvir/paritaprevir/ritonavir/dasabuvir, AbbVie) combined with Sovaldi (sofosbuvir, Gilead Sciences) have high levels of efficacy. Unfortunately, these combinations are quite expensive and are less accessible due to their unapproved status and lack of large pivotal trials that demonstrate their efficacy.
Vosevi was studied extensively in the POLARIS studies, of which there were four in total.
The two that have emerged as most relevant, because they evaluated the patient populations for which approval has been garnered, were POLARIS-1 and -4. In POLARIS-1, patients who previously failed an NS5A-containing DAA received Vosevi for 12 weeks. In POLARIS-4, the participants previously failed a DAA regimen that did not contain an NS5A inhibitor.
Of these two studies POLARIS-1 was more impactful because most patients who have been treated with DAA regimens so far have received an NS5A inhibitor. They have become foundational to the way we treat HCV in recent years. Only simeprevir/sofosbuvir, an early DAA combination used extensively in the early DAA era, falls into the POLARIS-4 category, but it is seldom used anymore.
POLARIS-1, demonstrated very high levels of efficacy for 12 weeks of SOF/VEL/VOX in patients with all genotypes who had been treated with an NS5A inhibitor previously. The comparator group was a placebo-recipient group which produced no SVRs.
The efficacy rate in the Vosevi group was 96% rate of SVR — 99% in those without cirrhosis and 93% in those with cirrhosis. There were six relapses in the cirrhosis group (n = 121) and no virologic failures in those without cirrhosis (n = 142).
A distinctive feature of this regimen that sets it apart from earlier regimens is that baseline resistance associated substitutions in the protease and NS5A domains did not affect efficacy. Moreover, the few patients who relapsed did not have treatment emergent resistant-associated substitutions. This leaves open the possibility, that deserves to be explored further, of whether repeated treatment with a longer duration of Vosevi with or without ribavirin might work in these failures.
In POLARIS 4, patients had failed DAAs that did not contain NS5A, so most of the patients had received sofosbuvir (85%) with or without a protease inhibitor. In POLARIS 4, the comparator group was 12 weeks of SOF/VEL.
Here there was a distinct advantage for 12 weeks of the triple regimen, with SVR rates of 97% vs 90% with SOF/VEL alone. It could be questioned why the results of SOF/VEL were distinctly under 95% in contrast to all other studies of POLARIS. This probably has something to do with the fact that whatever made patients fail a sofosbuvir-containing regimen previously, whether it’s a bioavailability issue, an absorption issue or something else, this likely underlies a failure to succeed with sofosbuvir that was presumably again at play despite the addition of velpatasvir. The numerically higher SVR12 rates with SOF/VEL/VOX versus SOF/VEL in POLARIS-4 were limited to patients with genotypes 1a and 3.
With regard to safety, there is a slight increase in GI side effects with Vosevi, most of which were mild, consisting of nausea or diarrhea, and resulted in no treatment discontinuations.
The results of POLARIS-1 and -4 garnered FDA approval in July 2017, for 12 weeks of Vosevi in patients with genotypes 1 through 6, with or without compensated cirrhosis, who failed a regimen with an NS5A inhibitor, and for patients who had failed a sofosbuvir-containing regimen, without an NS5A, with genotypes 1a and 3. It should be underscored that Vosevi is only approved for compensated cirrhosis at this point; protease inhibitors are either not recommended or contraindicated in child’s B or C patients across the board due to pharmacokinetic considerations.
In my practice, we have already recalled the few patients who failed DAA regimens with the intention to offer them this regimen.
Worthy of mention are the POLARIS-2 and -3 studies in DAA-naive patients. POLARIS-2 compared 8 weeks of SOF/VEL/VOX 12 weeks of SOF/VEL in more than 900 patients with genotypes 1 through 6 except for genotype 3 patients with cirrhosis, and demonstrated SVR12 rates of 95% and 98%. The SVR12 rate in the triple therapy group failed to meet the protocol-specified noninferiority endpoint, a difference in efficacy driven almost entirely by lower SVR12 rates with triple therapy in the genotype 1a patients. Curiously, the Q80K protease polymorphism highly prevalent in genotype 1a, which historically reduced efficacy of the protease inhibitor simeprevir with pegylated interferon and ribavirin, was associated with lower SVR12 rates in the genotype 1a patients of POLARIS-2, even though the sensitivity of the Q80K-containing virus is not reduced in vitro to voxilaprevir as it was to simeprevir. The reason for the divergent results in the genotype 1a patients between the two treatment arms in POLARIS-2 remains unclear. In POLARIS-3, containing exclusively genotype 3 patients with cirrhosis, the trial design was identical and so were the SVR12 rates: 96% with 8 weeks of SOF/VEL/VOX and 12 weeks of SOF/VEL. Thus, SOF/VEL/VOX is an excellent genotype 3 regimen, but because it was equivalent to SOF/VEL in efficacy, rather than superior, it did not garner regulatory approval for this group of patients nor for the larger population of genotypes 1 through 6 DAA-naive patients.
Mavyret (glecaprevir/pibrentasvir, AbbVie) is a novel second generation regimen that includes two drugs: glecaprevir, a protease inhibitor, and pibrentasvir, an NS5A inhibitor. Both of these are true second-generation drugs individually, so this is a true second-generation regimen. This means they are pan-genotypic and they cover the resistance variants particular to the protease class and the NS5A class that confer loss of sensitivity in vitro or have characterized the viral populations of patients who have failed first generation regimens.
The Mavyret studies included a broad spectrum of patients — cirrhotics, non-cirrhotics, treatment-naive, interferon failures, DAA failures, HIV coinfection, renal failure, kidney and liver transplants. However, patients with decompensated cirrhosis were not included. This regimen, which has been abbreviated as G/P regimen, was studied without ribavirin.
One of the largest of these phase 3 trials was the ENDURANCE-1 study, which evaluated patients without cirrhosis receiving 8 weeks of therapy vs. 12 weeks of therapy. Patients could be either interferon-experienced or treatment-naive.
The SVR rates were 99.1% in more than 300 patients who received 8 weeks of therapy and 99.8% in the patients who received 12 weeks of therapy. These SVR rates reflect only one virologic failure in the 8-week group and none in the 12-week group.
Genotype 3 was studied in a separate study called ENDURANCE-3, which compared 8 or 12 weeks of G/P vs. 12 weeks daclatasvir plus sofosbuvir and showed statistically noninferior SVR rates of 95% for each of the two Mavyret regimens and 97% for daclatasvir plus sofosbuvir, though there were a few more relapsers in the Mavyret groups.
The ENDURANCE-2 and -4 studies evaluated 12 weeks of G/P in patients with genotype 2 and genotype 4 through 6, respectively with SVR rates of 99% in each study. In SURVEYOR-2, part 4, an 8-week regimen of G/P was studied in patients with genotypes 2, 4, 5 and 6 without cirrhosis with SVR 12 rates by modified intent-to-treat analysis of 98% to 100%. In EXPEDITION-1, the G/P regimen proved to be robust in patients with compensated cirrhosis, with an overall SVR rate of 99% in patients with genotypes 1, 2, 4 and 5. In patients with all genotypes and renal impairment, studied for 12 weeks with G/P there were no virologic failures in 104 patients. The regimen also proved to be robust in studies evaluating HIV/HCV coinfected patients, patients with renal impairment (with zero virologic failures out of 104 patients given G/P), and patient with renal or liver transplants.
In MAGELLAN-1, part 2, which evaluated Mavyret in patients with prior DAA failure, the regimen did very well except in patients who had been exposed to both a protease and an NS5A inhibitor, the latter finding attributable to the presence of dual class resistance substitutions. Most of the DAA-failure patients studied had genotype 1. Therefore this regimen is approved for the treatment of patients with genotype 1, who previously received a regimen containing an NS5A inhibitor or an NS3/4A protease inhibitor, but not both.
Overall, the results with G/P are very robust and established 8 weeks of G/P as a newly approved regimen, as of August 2017, for non-cirrhotic patients with all HCV genotypes. Although not the first approved 8-week regimen — that distinction belonging to Harvoni (ledipasvir/sofosbuvir, Gilead Sciences) — G/P is approved for 8 weeks in interferon-experienced patients as well as treatment-naive patients across all genotypes and is independent of the patient’s baseline viral load. Many clinicians value the concept of giving the shortest duration of therapy necessary without sacrificing SVR. Additionally, the regimen is approved for 12 weeks in cirrhosis and is highly efficacious.
We do have to be mindful of drug-drug interactions and clinicians would be well advised to review that list. There is no issue with proton-pump inhibitors.
The availability of the first approved regimens in DAA failure patients, although affecting relatively few patients because of the high SVR rates with existing regimens, is a major advance toward the universal goal of “leaving no patient behind” without cure of their HCV. The data base from phase 3 trials for SOF/VEL/VOX is larger for DAA-failure patients than for G/P, and the approved DAA-failure is more expansive, with no genotype restrictions, a uniform duration of treatment of 12 weeks (vs. 16 weeks for G/P in prior NS5A treatment failures), and applicability to patients who have been exposed to both protease and NS5A inhibitors. Further data on G/P in DAA failures would be valuable and plans are in progress to obtain such data, and even for SOF/VEL/VOX we will have to explore approaches for 12-week failures, which among NS5A-experienced patients was confined to cirrhotics in the POLARIS-1 trial. Perhaps simply retreating for a longer time will suffice, given the lack of impact of baseline RASs on outcome with this regimen and the infrequency of treatment-emergent RASs in the few patients who fail.
With the G/P regimen we have a highly effective new option for 8-week treatment, in patients who are non-cirrhotic and DAA-naive. Clinicians will have to decide whether the capacity to shorten the duration of therapy is significant for them and their patients, but many clinicians have expressed the feeling that so long as there is no discernible impact on SVR, a shorter duration of treatment would be viewed favorably. Reduced costs, if facilitated by a shorter duration regimen, may also result in expanded access to therapy nationally and internationally. Whether in cirrhotics treated with 12 weeks of G/P, HIV/HCV coinfected patients or patients with renal or liver transplants, the efficacy of G/P appears to be excellent, and the regimen is very attractive for patients with renal impairment (sofosbuvir for patients with GFR <30 ml/min is still unapproved).
Finally, no discussion of the POLARIS studies would be complete without acknowledging the affirmation in these studies of the very high level of efficacy of SOF/VEL demonstrated in the previous ASTRAL studies, which led to its approval in 2016. This efficacy was reaffirmed abundantly in the studies of SOF/VEL/VOX, in which 12 weeks of SOF/VEL performed very well when compared to the triple regimen in DAA-naive patients.
All in all, we are living in a time when we can still marvel at our abilities to cure nearly every single patient with HCV who walks into our offices. These approvals and expansions further our ongoing goal of eradicating HCV.
Ira M. Jacobson, MD
Co-Chief Medical Editor
- Bourliére M, et al. N Engl J Med. 2017;doi:10.1056/NEJMoa1613512.
- Forns X, et al. Lancet Infect Dis. 2017:doi: 10.1016/S1473-3099(17)30496-6.
- Foster GR, et al. Abstract GS-007. Presented at: International Liver Congress; April 19-24, 2017; Amsterdam.
- Gane EJ, et al. Abstract LB-11. Presented at: The Liver Meeting; Nov. 11-15, 2016; Boston.
- Jacobson IM, et al. Abstract LB-12. Presented at: The Liver Meeting; Nov. 11-15, 2016; Boston.
- Lawitz E, et al. Hepatol. 2017;doi:10.1002/hep.29130.
- Poordad F, et al. Hepatol. 2017;doi:10.1002.hep.29081.
- Reau N, et al. Abstract LBO-03. Presented at: International Liver Congress; April 19-24, 2017; Amsterdam.
Disclosures: Jacobson reports consulting for AbbVie, Achillion, Bristol- Myers Squibb, Gilead, Intercept, Janssen, Merck and Trek; receiving grant or research support from AbbVie, Bristol-Myers Squibb, Gilead, Janssen and Merck; and speaking and teaching for AbbVie, Bristol-Myers Squibb, Gilead and Janssen.