New Findings from Study Evaluating Islatravir in Combination with Doravirine versus DELSTRIGO™ (doravirine 100 mg/3TC 300 mg/tenofovir disoproxil fumarate 300 mg)
Company Plans to Initiate Phase 3 Trials
KENILWORTH, NJ, USA I July 24, 2019 I Merck (NYSE: MRK), known as MSD outside the United States and Canada, announced the results from a Phase 2b clinical trial evaluating the efficacy, tolerability, and safety of islatravir (MK-8591), the company’s investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI), for the treatment of HIV-1. The trial evaluated three oral, once-daily doses of islatravir initially for 24 weeks in combination with Merck’s doravirine** (a non-nucleoside reverse transcriptase inhibitor [NNRTI]) plus lamivudine (3TC, 300 mg), and then for a further 24 weeks in combination with doravirine, compared to DELSTRIGO™ (doravirine 100 mg/3TC 300 mg/tenofovir disoproxil fumarate 300 mg) in adults with HIV-1 infection who had not previously received antiretroviral treatment. At all dose levels, the combination of islatravir and doravirine maintained antiviral activity as measured by the number of study participants achieving HIV-1 RNA levels <50 copies/mL, similar to DELSTRIGO at Week 48 of the study. These findings were presented as a late-breaking oral presentation (Abstract WEAB0402LB) at the 10th International AIDS Society Conference on HIV Science (IAS 2019) in Mexico City and featured in the official IAS 2019 press program.
“These results provide evidence for the antiviral properties of islatravir in combination with doravirine as a potential once-daily dual regimen for people living with HIV-1,” said Dr. Jean-Michel Molina, Professor of Infectious Diseases at Paris Diderot University and Head of the Infectious Diseases Department, Saint-Louis Hospital, Paris, the study’s lead investigator. “There is a continuing need for additional efficacious therapeutic regimens for the treatment of people living with HIV-1, and islatravir warrants further study.”
Based on these data, Merck plans to initiate a Phase 3 program evaluating islatravir in combination with doravirine across diverse patient populations to address the evolving needs of people living with HIV-1.
PIFELTRO (doravirine, 100 mg) is indicated in combination with other ARV agents for the treatment of HIV-1 infection in adult patients with no prior ARV treatment history. DELSTRIGO (doravirine 100 mg/3TC 300 mg/tenofovir disoproxil fumarate 300 mg) is indicated as a complete regimen for the treatment of HIV-1 infection in adult patients with no prior ARV treatment history. DELSTRIGO contains a boxed warning regarding post-treatment acute exacerbation of hepatitis B (HBV) infection. DELSTRIGO and PIFELTRO do not cure HIV-1 infection or AIDS.
DELSTRIGO and PIFELTRO are contraindicated when co-administered with drugs that are strong cytochrome P450 (CYP)3A enzyme inducers (including the anticonvulsants carbamazepine, oxcarbazepine, phenobarbital, and phenytoin; the androgen receptor inhibitor enzalutamide; the antimycobacterials rifampin and rifapentine; the cytotoxic agent mitotane; and the herbal product St. John’s wort (Hypericum perforatum)) as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of DELSTRIGO and PIFELTRO. DELSTRIGO is contraindicated in patients with a previous hypersensitivity reaction to 3TC. For more information, see “Selected Safety Information” below.
“We are eager to build upon the findings of this Phase 2b study of islatravir,” said Dr. George Hanna, vice president and therapeutic area head of infectious diseases, global clinical development, Merck Research Laboratories. “Data presented at this meeting underscores Merck’s commitment to evaluate the potential of islatravir for the treatment and pre-exposure prophylaxis of HIV-1.”
Phase 2b Study Results for Investigational 2-Drug Regimen of Islatravir with Doravirine
In this international, multicenter clinical trial, adult participants with HIV-1 infection who had not previously received antiretroviral therapy (treatment-naïve) were randomly assigned (1:1:1:1) to one of four once-daily treatment groups: islatravir 0.25 mg (n=29), 0.75 mg (n=30) or 2.25 mg (n=31) in combination with doravirine (100 mg) and 3TC (300 mg) compared to DELSTRIGO (n=31). After a minimum of 24-weeks of treatment, participants in the islatravir treatment groups with HIV-1 RNA levels less than 50 copies/mL who had not met any protocol defined virologic failure (PDVF) criteria were transitioned to a 2-drug regimen consisting of the same dose of islatravir plus doravirine (100 mg), without 3TC.
Results showed that the participants who received islatravir in combination with doravirine plus 3TC for 24 weeks, and switched to islatravir in combination with doravirine, demonstrated efficacy at Week 48 as measured by HIV-1 RNA <50 copies/mL, similar to DELSTRIGO (FDA snapshot approach) (see table 1). The antiretroviral activity observed at Week 48 was consistent with study findings at Week 24, which were also presented at IAS 2019 (Abstract LBPED46), showing comparable antiviral activity for all islatravir treatment groups versus DELSTRIGO, regardless of HIV-1 RNA level at baseline. The Phase 2b study continues with additional measures to be taken at Week 96 and beyond.
Table 1 Efficacy Results
| 0.25 mg islatravir* containing regimen | 0.75 mg islatravir* containing regimen |
2.25 mg islatravir* containing regimen |
DELSTRIGO (n=31) | |||||
| 24wk | 48wk | 24wk | 48wk | 24wk | 48wk | 24wk | 48wk | |
| HIV-1 RNA copies <50 copies/mL (FDA snapshot) |
89.7% (26/29) |
89.7% (26/29) |
100% (30/30) |
90% (27/30) |
87.1% (27/31) |
77.4% (24/31)
|
87.1% (27/31) |
83.9% (26/31)
|
*Participants initially received islatravir +doravirine+3TC and switched to islatravir+ doravirine.
Table includes participants who discontinued because of adverse event (AE) at any time point from Day 1 through the time window, if this resulted in no virologic data on treatment during the specified window. Additional reasons include: lost to follow-up, physician decision, protocol deviation, withdrawal by subject.
Protocol-defined virologic failure (PDVF), defined as rebound with confirmed HIV-1 RNA greater than or equal to 50 copies/mL after suppression or non-response with confirmed HIV-1 RNA greater than or equal to 50 copies/mL at Week 48, was confirmed in six participants, 5.6% (5/90; 4 rebound, 1 non-response) of the islatravir treatment groups combined and 3.2% (1/31; rebound) of the DELSTRIGO group. However, all participants with PDVF had confirmatory HIV-1 RNA levels < 80 copies/mL.
No serious drug-related adverse events (AE) were reported for any islatravir treatment group at Week 48. The most common reported adverse events (reported by >10% participants) in the DELSTRIGO-treated group (31pts) were diarrhea (16.1%), bronchitis (12.9%) and syphilis (12.9%). The most common reported adverse events (reported by >10% participants) in the islatravir-treated groups were: 0.2 mg (29 pts) (sinusitis, pain in extremity, headache – 10.3%, 10.3% and 13.8%, respectively); 0.75 mg (30 pts) (diarrhea, nausea, bronchitis, nasopharyngitis, syphilis, vitamin D deficiency -13.3%, 13.3%, 13.3%, 13.3%, 10.0%, 13.3%, respectively); 2.25 mg (31pts) (arthralgia, headache – 12.9%, 12.9%, respectively). One serious drug-related AE resulted in discontinuation in a participant in the DELSTRIGO group. Two participants in the islatravir-treated dose groups (both 2.25 mg) discontinued due to an AE.
About the Islatravir/Doravirine Phase 2b Trial
This Phase 2b randomized, double-blind, active-comparator-controlled, dose-ranging clinical trial evaluated the safety, tolerability, antiretroviral activity and pharmacokinetics of islatravir in combination with doravirine and lamivudine (3TC) in treatment-naïve adults with HIV-1 infection with baseline HIV-1 RNA ≥1,000 copies/mL and CD4+ T-cell count >200 cells/mm3. At week 24 of treatment, participants receiving an islatravir-containing regimen who achieved HIV-1 RNA level copies less than 50 copies/mL and did not reach criteria for PDVF resistance were transitioned to an islatravir and doravirine combination regimen for a further 24 weeks.
The primary efficacy endpoints of the study were the proportion of participants with HIV-1 RNA copies less than 50 copies/mL at Week 24 and Week 48. The primary safety endpoints were number of participants experiencing adverse events and discontinuations due to adverse events. The Phase 2b study continues with additional measures to be taken at Week 96 and beyond. For further information, please visit www.clinicaltrials.gov (NCT03272347).
About Islatravir
Islatravir is Merck’s investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) currently being evaluated in clinical trials for the treatment of HIV-1 infection in combination with other antiretrovirals, as well as for pre-exposure prophylaxis (PrEP) of HIV-1 infection as a single investigational agent across a variety of formulations.
About Doravirine
Doravirine is currently marketed in the United States and other jurisdictions as PIFELTRO, and in a fixed-dose combination tablet with 3TC and tenofovir disoproxil fumarate (TDF) as DELSTRIGO. PIFELTRO (doravirine, 100 mg) is a once-daily non-nucleoside reverse transcriptase inhibitor (NNRTI) to be administered in combination with other antiretroviral (ARV) medicines. DELSTRIGO is a once-daily fixed-dose combination tablet of doravirine (100 mg), lamivudine (3TC, 300 mg) and tenofovir disoproxil fumarate (TDF, 300 mg) as a complete regimen. PIFELTRO and DELSTRIGO were approved in 2018 for the treatment of HIV-1 infection in adult patients not previously treated with antiretroviral therapy. A supplemental New Drug Application (sNDA) is under review by the FDA for use (in combination with other antiretrovirals) in people living with HIV-1 who are switching from a stable antiretroviral regimen and whose virus is suppressed (HIV-1 RNA <50 copies/mL). The Prescription Drug User Fee Act (PDUFA) date for the sNDA is Sept. 20, 2019.
Our Commitment to HIV
For more than 30 years, Merck has been committed to scientific research and discovery in HIV, and we continue to be driven by the conviction that more medical advances are still to come. Our focus is on pursuing research that addresses unmet medical needs and helps people living with HIV and their communities. We remain committed to working hand-in-hand with our partners in the global HIV community to address the complex challenges that hinder continued progress.
About Merck
For more than a century, Merck, a leading global biopharmaceutical company known as MSD outside of the United States and Canada, has been inventing for life, bringing forward medicines and vaccines for many of the world’s most challenging diseases. Through our prescription medicines, vaccines, biologic therapies and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to health care through far-reaching policies, programs and partnerships. Today, Merck continues to be at the forefront of research to advance the prevention and treatment of diseases that threaten people and communities around the world – including cancer, cardio-metabolic diseases, emerging animal diseases, Alzheimer’s disease and infectious diseases including HIV and Ebola. For more information, visit www.merck.com and connect with us on Twitter, Facebook, Instagram, YouTube and LinkedIn.
SOURCE: Merck
