What You Don’t Know, You Can Sell
tagline Spring 2012<https://www.treatmentactiongroup.org/tagline/2012/spring/tagline/2012/spring>
by Tracy Swan
In places where access to antiretroviral therapy is widespread, people
living with HIV are now dying from a common and curable coinfection:
hepatitis C virus (HCV). HIV increases the risk for, and accelerates the
rate of, liver disease from hepatitis C. Pegylated interferon and
ribavirin, medications used to treat HCV, are less effective in people with
HIV than in their HCV-monoinfected counterparts.
In 2011, the first hepatitis C protease inhibitors, Merck’s boceprevir and
Vertex’s telaprevir, were approved based on trials in people with hepatitis
C monoinfection. Both drugs are being studied in coinfected people, thanks
to pressure from the international HIV/HCV community and encouragement from
regulatory agencies.
Despite outrage from activists, Merck refused to study drug-drug
interactions (DDIs) between boceprevir (Victrelis), their HCV protease
inhibitor, and drugs commonly used to treat HIV, putting coinfected study
volunteers at risk for drug-drug interactions in their own clinical trial.
Drug-drug interactions can have serious consequences for HIV/HCV-coinfected
people, who risk forfeiting current and future treatment options for HIV
and possibly HCV as well. DDIs can lower drug concentrations to an
ineffective level, leading to drug resistance, or increase drug
concentrations, worsening side effects and leading to treatment
discontinuation; they can even be life-threatening, as was the case with
ribavirin and didanosine (DDI; Videx).
The boceprevir coinfection study opened in mid-2009, before Merck had
performed drug-drug interaction studies with HIV protease inhibitors in
healthy volunteers, a common step in drug development. Nonetheless,
coinfected study volunteers were allowed to use them; in fact, by default,
HIV protease inhibitors— or Merck’s own integrase inhibitor, raltegravir
(Isentress)—were the only HIV treatment options for study volunteers, since
non-nucleoside reverse transcriptase inhibitors were not allowed. Activists
kept asking Merck to perform DDIs throughout boceprevir’s development, but
Merck’s attitude remained cavalier; they did not launch key drug-drug
interaction studies until two years later, months after boceprevir was
approved.
The results of DDI studies with three ritonavir-boosted HIV protease
inhibitors, atazanavir/r (Reyataz), darunavir/r (Prezista), and lopinavir/r
(Kaletra) in healthy volunteers (rather than the actual trial participants
who were using boceprevir with HIV protease drugs for almost a year) were
presented in March at the 19th Conference on Retroviruses and Opportunistic
Infections (CROI) in Seattle. The news was not good. Combining boceprevir
with these HIV protease inhibitors lowered concentrations of each HIV
protease inhibitor, at both the highest and lowest (peak and trough) levels.
Boceprevir lowered the peak concentration of atazanavir/r by 25 percent,
and the trough by 49 percent; darunavir/r peak decreased by 36 percent and
trough by 59 percent; for lopinavir/r, coadministration with boceprevir
dropped the peak concentration by 30 percent and trough by 43 percent. In
turn, boceprevir levels dropped by 45 percent when coadministered with
lopinavir/r and by 32 percent when administered with daruanvir/r; only
atazanavir/r had no effect on the concentration of boceprevir.
Failure to characterize these drug-drug interactions put study
participants—and coinfected patients— at an unacceptable level of risk,
although clinical implications—or real-life impact on HIV and hepatitis C
treatment outcomes—of these drug interactions are not clear. Nonetheless,
the U.S. Food and Drug Administration warned that “drug interactions
between the hepatitis C virus (HCV) protease inhibitor Victrelis
(boceprevir) and certain ritonavir-boosted human immunodeficiency virus
(HIV) protease inhibitors (atazanavir, lopinavir, darunavir) can
potentially reduce the effectiveness of these medicines when they are used
together.”
Regulators from the European Medicines Agency’s (EMA) Committee for
Medicinal Products for Human Use (CHMP) went a step further, recommending
that “doctors treating patients co-infected with hepatitis C and HIV should
be aware of the findings of the drug interaction study. They should not
co-administer Victrelis with ritonavir-boosted darunavir or lopinavir in
HIV and hepatitis C co-infected patients. Co-administration of Victrelis
with ritonavir-boosted atazanavir may be considered on a case-by-case basis
if deemed necessary in patients with suppressed HIV viral loads and with an
HIV strain without any suspected resistance to the HIV regimen. Increased
clinical and laboratory monitoring is warranted.”
Vertex’s rival protease inhibitor, telaprevir (Incivek) has outsold
boceprevir: in the fourth quarter of 2011, telaprevir trounced boceprevir
$456.8 million to $87 million. The opportunity to capture the coinfection
market share may have motivated Merck’s decision to delay drug-drug
interaction studies. HCV is more likely to be diagnosed and treated in
HIV-positive people than people with HCV alone, for several reasons. HIV
treatment guidelines recommend HCV testing for all HIV-positive people; the
infrastructure to deliver treatment is already in place; and hepatitis C is
known to be more aggressive in people with HIV, so physicians and patients
are more game to try for a cure.
After Vertex reported drug interactions between telaprevir and ritonavir
boosted HIV protease inhibitors, boceprevir became a more attractive option
for co-infected people. Merck’s vice president of clinical research, Robin
Issacs, alluded to off-label use in the company’s February 8 press release.
“Though VICTRELIS is not indicated for the treatment of chronic HCV in
those who are also infected with HIV, we recognize that some physicians
have prescribed or may be considering prescribing VICTRELIS for patients
taking ritonavir-boosted HIV protease inhibitors. We felt it was important
to share these data as part of our commitment to patient safety and
transparency.”
*Where was Merck’s commitment to safety during boceprevir’s development? We
can only hope that no patients have been harmed.*
The boceprevir experience underscores the importance of timely DDI studies.
There are other medications used by people with hepatitis C—whether or not
they are coinfected with HIV—that warrant study, such as methadone,
buprenorphine, and commonly prescribed psychiatric medications. Merck
representatives have stated that the company will be more proactive with
their promising second-generation hepatitis C protease inhibitor, MK-5172.
Activists have released a
statement<https://www.treatmentactiongroup.org/hcv/2012/hepatitis-c-drug-development-and-drug-drug-interaction-studies>
calling
on regulatory agencies and pharmaceutical companies to study DDIs between
experimental HCV drugs that are broken down by the body in a similar way
with hormonal contraceptives, methadone, buprenorphine, lipid lowering
agents, immunosuppressive drugs, herbal remedies, and commonly prescribed
psychiatric medications in addition to HIV medications. •
