Hepatitis C: it's a long way to new therapy, it's a long way to go

Recombinant interferon-Beta-1alpha plus ribavirin for the treatment of chronic HCV infection: a prospective, randomized, comparative pilot study

BACKGROUND/AIMS

Interferon beta (IFN-beta) has been shown to have antiviral activity, and thus could be useful in treating viral infections. Therefore, we compared the efficacy and safety of recombinant IFN-beta (IFN-beta-1a) plus oral ribavirin versus interferon alpha (IFN-alpha) plus ribavirin therapy for the treatment of chronic hepatitis C (HCV).

METHODS

Twenty treatment-naïve patients were randomized into two equal-sized treatment groups. Both IFN-beta-1a (44 microg) and IFN-alpha (3 MIU) were given subcutaneously three times a week, while ribavirin was given orally at 1,000-1,200 mg/day. Patients were treated for 24 weeks and followed for an additional 24 weeks.

RESULTS

After 24 weeks of treatment, six (60%) and four patients (40%) in the IFN-beta-1a group and IFN-alpha groups, respectively, achieved viral clearance. The sustained virological response (SVR) at the end of the observation period was similar in both groups (40%). However, the baseline viral load was significantly higher (p=0.034) in the IFN-beta-1a group than in the IFN-alpha group, and there were more HCV genotype 1 patients in the IFN-beta-1a group (eight versus seven). The IFN-beta-1a group was associated with similar adverse events in terms of frequency and severity.

CONCLUSIONS

The SVR rate and safety profile were similar for the combination of IFN-beta-1a and ribavirin and that of IFN-alpha and ribavirin.

Preclinical characteristics of the hepatitis C virus NS3/4A protease inhibitor ITMN-191 (R7227)

Future treatments for chronic hepatitis C virus (HCV) infection are likely to include agents that target viral components directly. Here, the preclinical characteristics of ITMN-191, a peptidomimetic inhibitor of the NS3/4A protease of HCV, are described. ITMN-191 inhibited a reference genotype 1 NS3/4A protein in a time-dependent fashion, a hallmark of an inhibitor with a two-step binding mechanism and a low dissociation rate. Under preequilibrium conditions, 290 pM ITMN-191 half-maximally inhibited the reference NS3/4A protease, but a 35,000-fold-higher concentration did not appreciably inhibit a panel of 79 proteases, ion channels, transporters, and cell surface receptors. Subnanomolar biochemical potency was maintained against NS3/4A derived from HCV genotypes 4, 5, and 6, while single-digit nanomolar potency was observed against NS3/4A from genotypes 2b and 3a. Dilution of a preformed enzyme inhibitor complex indicated ITMN-191 remained bound to and inhibited NS3/4A for more than 5 h after its initial association. In cell-based potency assays, half-maximal reduction of genotype 1b HCV replicon RNA was afforded by 1.8 nM; 45 nM eliminated the HCV replicon from cells. Peginterferon alfa-2a displayed a significant degree of antiviral synergy with ITMN-191 and reduced the concentration of ITMN-191 required for HCV replicon elimination. A 30-mg/kg of body weight oral dose administered to rats or monkeys yielded liver concentrations 12 h after dosing that exceeded the ITMN-191 concentration required to eliminate replicon RNA from cells. These preclinical characteristics compare favorably to those of other inhibitors of NS3/4A in clinical development and therefore support the clinical investigation of ITMN-191 for the treatment of chronic hepatitis C.

Which patients with genotype 1 chronic hepatitis C can benefit from prolonged treatment with the 'accordion' regimen?

The on-treatment virological response to pegylated interferon plus ribavirin therapy is a useful tool in the management of patients with chronic hepatitis C. The time at which hepatitis C virus RNA becomes undetectable by a sensitive PCR assay has a huge impact on the probability of achieving a sustained virological response, particularly in genotype 1 patients, and may be useful in selecting patients for prolonged therapy. Indiscriminate extension of treatment in patients with hepatitis C virus genotype 1 is not beneficial. However, there is a subgroup of patients - the so-called 'slow responders' - who benefit from extending treatment from 48 to 72 weeks and can be readily identified after 4-12 weeks of combination therapy. Thus, it is important to distinguish slow responders from null responders. In the TeraVIC-4 study virological relapse rates were significantly lower, and sustained virological response rates were significantly higher, in those treated for 72 weeks with peginterferon alfa-2a (40 kDa) plus ribavirin (45% vs. 32% with 48 weeks, P=0.014). Patients are best served by quantitative determination of the hepatitis C virus RNA level at weeks 4, 12 and 24. The results of these determinations can then be used to tailor the length of therapy.

Hepatitis C virus population dynamics during infection

Hepatitis C virus (HCV) behaves as an evolving viral quasispecies in its continuously changing environment. The study of HCV quasispecies population dynamics in experimental models and infected patients can provide useful information on factors involved in the HCV life cycle and pathogenicity. HCV quasispecies variability also has therapeutic implications, as the continuous generation and selection of fitter or truly resistant variants can allow the virus to escape control by antiviral drugs.