GlaxoSmithKline plc / Concert Pharmaceuticals, Inc.

HIV-1 Infection (deuterium-modified protease inhibitor)

Disease Overview

HIV-1 protease inhibitors (PIs) block viral maturation and remain a backbone of antiretroviral therapy for treatment-experienced and select treatment-naive patients. PIs almost universally require co-dosing with a CYP3A4 'booster' (ritonavir or cobicistat) to achieve therapeutic exposure, adding pill burden, drug-drug interactions and tolerability issues.

Competitive Landscape

In 2009 the boosted-PI class was anchored by atazanavir (Reyataz, BMS) and lopinavir/ritonavir (Kaletra, Abbott), with darunavir (Prezista, J&J/Tibotec) as the newer entrant and once-daily integrase inhibitors (raltegravir/Isentress, Merck) reshaping first-line regimens. CTP-518 was a deuterated analog of atazanavir designed by Concert Pharmaceuticals — the lead asset in the GSK alliance — with the goal of slowing CYP3A4-mediated metabolism enough to eliminate the ritonavir boost, an unmet need across the entire class. The deal terms — $35M upfront including a $16.7M GSK equity investment, plus up to ~$1B in milestones across three Concert programs (CTP-518, a preclinical CKD compound, and a third) and three GSK pipeline compounds receiving deuterium modification — represented one of the first large pharma validations of deuterium chemistry as a development strategy. What the deal changed: it gave Concert capital and a marquee pharma anchor, but CTP-518 was ultimately discontinued without reaching late-stage development as the HIV market shifted decisively toward integrase-inhibitor-based regimens (Stribild, Triumeq) that obviated the boosting problem entirely.