Step Pharma presents promising cancer treatment

Since September 2022, STP938, the cancer inhibitor developed by Step Pharma SAS, has been undergoing clinical trials for the treatment of T and B cell lymphoma. Now, Step Pharma, the French pharmaceutical company developing oral drugs to inhibit the cytidine triphosphate synthase 1 (CTPS1), presented their data on their CTPS1 inhibitor STP938 at the 64th American Society of Hematology Annual Meeting (ASH) that is currently taking place in the United States.  

CTP synthase 1 (CTPS1) is needed by all dividing cells for DNA synthesis. CTP synthase (CTPS) is a critical regulatory enzyme in nucleotide metabolism, catalyzing the rate-limiting step in de novo CTP synthesis part of de novo pyrimidine synthesis pathway that catalyses the conversion of uridine triphosphate (UTP) to cytidine triphosphate (CTP). CTP is a key building block for the production of DNA, RNA and some phospholipids. The two human CTPS isoforms, CTPS1 and CTPS2, share 75% sequence identity but have distinct physiological roles. While CTPS2 is uniformly expressed across various tissue types, CTPS1 expression is generally low but is up-regulated in activated T cells. Inhibiting CTPS1 without affecting CTPS2 is therefore a promising strategy for treating autoimmune disorders and T cell cancers while avoiding off-target effects. STP938, is an orally bioavailable inhibitor of CTPS1. It has a substantial anti-tumour impact in preclinical models of mantle cell lymphoma and multiple myeloma, and it displays synergistic anti-tumour action in preclinical models when paired with selective inhibitors of other pathways. The data presented today hold the promise that the CTPS1 inhibitor might become a treatment for a multitude of blood cancers, with the potential for accelerated approval from a single arm Phase II study.

“We are encouraged by the promising pre-clinical data produced by our collaborators showing the anti-tumour effects of STP938 in mantle cell lymphoma and multiple myeloma models,” said Andrew Parker, Chief Executive Officer of Step Pharma. “These data reinforce our conviction that by inhibiting CTPS1, a key component of the pyrimidine synthesis pathway to which all cancers are addicted, STP938 has broad therapeutic potential. We have commenced clinical trials to test the safety and efficacy of STP938 in T cell and B cell lymphomas to bring this potentially lifesaving therapy to patients in our efforts to drive a step change in the way we treat cancer.”