China-based Ascletis Pharma Inc. (HKEX: 1672) announced on Sunday that it has completed dosing its first patient in the United States phase one clinical trial of ASC61, an oral PD-L1 small molecule inhibitor prodrug, intended to treat advanced solid tumours.

This US Phase one trial, a dose-escalation study, is to assess the safety and tolerability of ASC61 and define the maximum tolerated dose (MTD) and recommended Phase two dose (RP2D) of ASC61 in patients with advanced solid tumours who have disease progression during or following standard therapy.

ASC61 is an oral small molecule inhibitor prodrug and its active metabolite, ASC61-A, is a potent and highly selective inhibitor which blocks PD-1/PD-L1 interaction by inducing PD-L1 dimerisation and internalisation.

The US phase one clinical trial is being carried out at Nebraska Cancer Specialists and California Cancer Centres and is likely to be completed by March 2023.