A Phase IIa Study Evaluating Safety, Pharmacokinetics, and Antiviral Activity of GSK2838232, a Novel, Second-generation Maturation Inhibitor, in Participants With Human Immunodeficiency Virus Type 1 Infection.

BACKGROUND: GSK2838232 is a second-generation, potent, small-molecule, oral human immunodeficiency virus type 1 (HIV-1) maturation inhibitor for once-daily administration boosted with a pharmacoenhancer. METHODS: The phase 2a, proof-of-concept study was an open-label, adaptive dose-ranging design. Safety, pharmacokinetics, and efficacy of GSK2838232 boosted by cobicistat were evaluated in individuals with HIV-1 infection. The study participants (N = 33) received GSK2838232 once daily across a range of doses (20-200 mg) with cobicistat 150 mg for 10 days. RESULTS: GSK2838232 was safe and well tolerated with no clinically meaningful changes in safety parameters or adverse events. Exposure (maximum concentration and area under the concentration-time curve from time zero to the concentration at 24 hours postdose) increased 2- to 3-fold with repeated dosing in an approximately dose-proportional manner, reaching steady-state by day 8 with a half-life (t½) from 16.3 to 19.2 hours. Clearance and t½ values were not dependent on dose. Viral load declined from baseline with all GSK2838232 doses. Mean maximum declines from baseline to day 11 in HIV-1 RNA log10 copies/mL with the 20-mg, 50-mg, 100-mg, and 200-mg cohorts were -0.67, -1.56, -1.32, and -1.70, respectively. CD4+ cell counts increased at doses ≥50 mg. CONCLUSIONS: GSK2838232 with cobicistat was well tolerated and exhibited efficacy as a short-term monotherapy in participants with HIV-1. This positive proof-of-concept study supports the continued development of GSK2838232 for the treatment of HIV as part of combination antiretroviral therapy. CLINICAL TRIALS REGISTRATION: NCT03045861.

Phase 1 Study of Molibresib (GSK525762), a Bromodomain and Extra-Terminal Domain Protein Inhibitor, in NUT Carcinoma and Other Solid Tumors.

BACKGROUND: Bromodomain and extra-terminal domain proteins are promising epigenetic anticancer drug targets. This first-in-human study evaluated the safety, recommended phase II dose, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of the bromodomain and extra-terminal domain inhibitor molibresib (GSK525762) in patients with nuclear protein in testis (NUT) carcinoma (NC) and other solid tumors. METHODS: This was a phase I and II, open-label, dose-escalation study. Molibresib was administered orally once daily. Single-patient dose escalation (from 2 mg/d) was conducted until the first instance of grade 2 or higher drug-related toxicity, followed by a 3 + 3 design. Pharmacokinetic parameters were obtained during weeks 1 and 3. Circulating monocyte chemoattractant protein-1 levels were measured as a pharmacodynamic biomarker. RESULTS: Sixty-five patients received molibresib. During dose escalation, 11% experienced dose-limiting toxicities, including six instances of grade 4 thrombocytopenia, all with molibresib 60-100 mg. The most frequent treatment-related adverse events of any grade were thrombocytopenia (51%) and gastrointestinal events, including nausea, vomiting, diarrhea, decreased appetite, and dysgeusia (22%-42%), anemia (22%), and fatigue (20%). Molibresib demonstrated an acceptable safety profile up to 100 mg; 80 mg once daily was selected as the recommended phase II dose. Following single and repeat dosing, molibresib showed rapid absorption and elimination (maximum plasma concentration: 2 hours; t1/2: 3-7 hours). Dose-dependent reductions in circulating monocyte chemoattractant protein-1 levels were observed. Among 19 patients with NC, four achieved either confirmed or unconfirmed partial response, eight had stable disease as best response, and four were progression-free for more than 6 months. CONCLUSIONS: Once-daily molibresib was tolerated at doses demonstrating target engagement. Preliminary data indicate proof-of-concept in NC.