Shares of Nektar Therapeutics Inc. tumbled 44.7% in premarket trading on Monday after the company said a combination of its experimental therapy bempegaldesleukin in combination with Bristol Myers Squibb Co.’s Opdivo failed as a treatment for melanoma. The companies had tested the combination against Opdivo in a Phase 3 clinical trial as a first-line treatment for patients with previously untreated unresectable or metastatic melanoma. After discovering the combination did not meet the study’s primary endpoints, they halted enrollment and unblinded the study. Nektar and Bristol are also evaluating bempegaldesleukin and Opdivo in patients with renal cell carcinoma and bladder cancer. Nektar’s stock is down 21.3% since the start of the year, while the broader S&P 500 has dropped 11.8%.
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