Sosei Group and Cancer Research UK have announced the first patient has been dosed in a Phase I/IIa clinical trial of pipeline drug HTL0039732 for advanced solid tumors.

The trial (NCT05944237) will evaluate Sosei’s oral small-molecule cancer immunotherapy drug HTL0039732. Cancer Research UK and Sosei Heptares signed an agreement in July 2022 to allow Cancer Research UK’s Centre for Drug Development (CDD) to sponsor, design and execute the trial.

The Phase I trial will define the toxicity, tolerability and pharmacokinetics of HTL0039732, identify the recommended dose for Phase II studies, and assess the antitumor activity as a monotherapy and combination therapy with the PD-L1 inhibitor atezolizumab. Phase IIa of the trial will expand the optimal combination dose in up to four cohorts in specified cancer indications.

First patients dosed in the UK

Patient recruitment has been initiated at Cambridge University Hospitals and Guy’s and St Thomas’ NHS Foundation Trusts in the UK. More sites will open across the Experimental Cancer Medicine Centre (ECMC) network.

The UK Medicines and Healthcare products Regulatory Agency (MHRA) has granted HTL0039732 an Innovation Passport, the first step in its Innovative and Licensing Access Pathway (ILAP), which aims to improve patient access to new medicines by reducing the time to market.

The MHRA grants Innovation Passports to medicines that treat life-threatening or seriously debilitating conditions, and where there is a significant patient or public health need.

How HTL0039732 works

HTL-0039732 acts as an EP4 antagonist. Targeting EP4 blocks the effects of PGE2 and increases the ability of the immune system to detect and control cancer cells. This makes HTL0039732 a potential candidate to treat patients with cancers that generally do not respond well to current immunotherapies.

The drug candidate is under development for the treatment of various cancers, including mesothelioma, sarcoma and pheochromocytoma.

CDD director Dr Nigel Blackburn said: “We are delighted to have reached this next significant milestone in our partnership with Sosei Heptares. The fact that immunotherapy works for some patients but not others means we desperately need more trials like this to open up potentially life-saving treatment options to more people.”