Ascletis Pharma Inc. (HKEX: 1672, "Ascletis") announces today the approval of the Investigational New Drug (IND) application by China National Medical Products Administration (NMPA) for the in-house developed oral PD-L1 small molecule inhibitor, ASC61, for the treatment of advanced solid tumors. While the ASC61 Phase I dose escalation study is ongoing in the U.S., IND approval in China will accelerate the global development of ASC61.

ASC61 is an oral small molecule inhibitor prodrug. Its active metabolite, ASC61-A, is a potent and highly selective inhibitor which blocks PD-1/PD-L1 interaction through inducing PD-L1 dimerization and internalization. As a single agent, ASC61 demonstrated significant antitumor efficacy in multiple animal models including humanized mouse model. Preclinical studies showed that ASC61 has good safety and pharmacokinetic profiles in animal models.  

In a head-to-head comparison study using the human PD-L1 expressing cells and fresh peripheral blood mononuclear cells (PBMCs) co-culture assay, ASC61-A treatment induced secretion of IFNγ in a concentration dependent manner, with an EC₅₀ of 2.86 nM. Maximal levels of IFNγ induced by ASC61-A were similar to that induced by Keytruda, a marketed PD-1 antibody.

Compared with PD-1/PD-L1 antibody injections, the oral PD-L1 inhibitor ASC61 has the following benefits: (1) higher patient compliance with easy and safe administration with no need of hospital visits for injections; (2) ease of all oral combination therapies with other oral anti-tumor drugs; (3) easier to manage immune-related adverse effects (irAEs) with dose adjustment; (4) relatively lower cost; and (5) higher permeability to distribute into targeted tissues.

"Immunogenicity and the poor permeability into tumor tissues are the major limitations of therapeutic antibodies, which can cause a low response rate of PD-1/PD-L1 antibodies. As a highly differentiated small molecule PD-L1 inhibitor, ASC61 showed promising safety profile in the dose escalation study in patients with advanced solid tumors in the U.S. so far.  With two IND approvals in the U.S. and China, we expect to accelerate the global development of ASC61 and provide more options for patients with advanced solid tumors." said Dr. Jinzi J. Wu, Founder, Chairman and CEO of Ascletis.