Gilead Sciences has bolted another asset onto the virology engine that powers the company, paying (PDF) Health Hope Pharma $10 million upfront for global rights to a candidate in a limited set of indications.
The deal will give Gilead exclusive global rights to the P-gp inhibitor encequidar in the virology space. In return, Gilead will pay HHP the upfront fee and commit up to $72.5 million in milestones. Hanmi Pharm, the original developer of the candidate, is also in line to receive an upfront fee and potential milestone payments tied to development, regulatory and sales events.
HHP is studying encequidar in combination with oral paclitaxel in cancer patients, with a phase 3 trial set to start this year. In that context, encequidar’s selective inhibition of P-gp in the gut could counter the drug transporter effect that typically prevents oral dosing of chemotherapeutics such as paclitaxel.
Gilead is yet to comment on how encequidar fits into its virology plans. Some antiviral drugs, including components of Gilead’s blockbuster Biktarvy, are substrates of P-gp. Giving such drugs at the same time as P-gp inhibitors can increase the absorption and plasma concentrations of the antiviral medicines.
Interactions between P-gp inhibitors and antiviral drugs can be undesirable. The label of Gilead’s Yeztugo recommends (PDF) against giving the twice-yearly HIV prevention drug with P-gp inhibitors. Yet there is also potential for co-administration with P-gp inhibitors to enhance the efficacy of antivirals that target pathogens including HIV and hepatitis C.
There is a long history of exploring P-gp inhibitors in such viral contexts. In 2001, a Roche scientist co-authored a paper about the potential for inhibitors of the drug transporter to improve HIV treatment by opening up pharmacological sanctuary sites such as the brain.
Gilead’s deal opens another chapter in encequidar’s long development journey. Hanmi out-licensed the candidate to Athenex in 2011. Athenex took the candidate as far as a filing for approval, only for the FDA to raise concerns about the safety and efficacy of the company’s oral paclitaxel formulation. After Athenex filed for bankruptcy in 2023, HHP bought a portfolio of cancer programs from the company.