Nektar Therapeutics Inc. shares dropped 35% in Monday morning trade after the company released early data from a phase 1/2 clinical trial testing the company’s NKTR-214 in combination with Bristol-Myers Squibb’s cancer drug Opdivo. Bristol-Myers shares declined nearly 1% premarket. The trial, which tested the safety and efficacy of the combination in patients with stage IV metastatic melanoma, renal cell carcinoma and urothelial cancers, had “underwhelming” results, said EvercoreISI analyst Josh Schimmer. “We remain unconvinced that ‘214 adds benefit to Opdivo,” he said. Noting that the companies did not separately present results for “stage 2” patients in the trial, he said, “if new cohort (N2) [overall response rate] doesn’t improve substantially with follow up, we expect investors to broadly lose confidence (if they haven’t already).” Drugmakers have been working to combine various cancer treatments in clinical trial to see if the combinations work better than one treatment on its own, and Bristol-Myers’ Opdivo is already a blockbuster cancer drug on its own accord. Not all analysts were so gloomy about Nektar’s NKTR-214, which is the company’s lead immuno-oncology drug candidate and is also being tested on its own and in combination with other drugs, though the Bristol-Myers collaboration is furthest along. The latest results, presented at the American Society of Clinical Oncology’s annual meeting, are “supportive of the long-term potential for NKTR-214 to enhance the efficacy of PD-1 in a number of tumor types,” said J.P. Morgan analyst Jessica Fye, “but expect near-term volatility based on immature response rate data (not entirely unexpected) that came in on the low end of Street expectations” and without an update on lung cancer patients. Nektar shares have dropped 43% over the last three months, and Bristol-Myers shares have dropped 22.5%, compared with a 1.6% rise in the S&P 500 and a 0.4% rise in the Dow Jones Industrial Average .