Merck is ending a clinical trial for berzosertib, an ATR inhibitor that was once considered a promising treatment in its oncology program.

The med that may be sent packing elsewhere is berzosertib, an ATR inhibitor that was in a phase 2 relapsed, platinum-resistant small cell lung cancer trial. EMD Serono conducted an interim analysis of the DDRiver SCLC 250 trial and found a low probability of success.

EMD Serono has decided to discontinue the trial, but “will continue its open innovation approach” that includes ongoing external studies of berzosertib in other combinations and clinical settings. The DDRiver SCLC 250 trial was assessing the med combined with the chemotherapy topotecan,

“While we did not see the outcomes we hoped for with this combination in this particularly challenging population of patients with platinum-resistant SCLC, we are confident in the potential of ATR inhibition, as a combination with chemotherapy is only one avenue to take advantage of DNA damage response,” said Victoria Zazulina, M.D., head of EMD Serono’s oncology development unit.

The company plans to “assess our path forward” with berzosertib, according to Zazulina, who pointed to another oral ATR inhibitor, M1774, and others in the company’s DNA damage response inhibitors program in the meantime.

But berzosertib had been the lead candidate in EMD Serono’s DNA damage response inhibitor pipeline, a type of cancer therapy that goes after existing defects in DNA repair. The therapy was also being tested in ovarian cancer and various solid tumors. Previously known as M6620, it was licensed from Vertex Pharmaceuticals in 2017. 

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