(Reuters) – Nektar Therapeutics said on Friday some patients with advanced bladder cancer treated with a combination of its experimental treatment and Bristol-Myers Squibb Co’s immunotherapy, Opdivo, showed signs of tumor reduction in an early-stage study.

Of the 27 patients with urothelial cancer, 19 percent showed complete response after being treated with the combo therapy using Nektar’s NKTR-214, according to data, which was presented at the Genitourinary Cancers Symposium in San Francisco.

The disease, which can infect any part of the urinary tract including the renal pelvis and the bladder, is the sixth most common type of cancer in the United States, the company said.

The treatment triggered response in 48 percent of 27 patients, the company said. Seven out of 16 patients who where ineligible for anti-cancer cisplatin chemotherapy showed signs of tumor reduction, while the same effect was seen in six of the 11 patients who refused the standard of care.

“When you understand that more than 50 percent of patients are not eligible for cisplatin-based chemotherapy, I think there is an unmet need (in treatment of these patients),” Arlene Siefker-Radtke, the principal investigator of the trial, told Reuters.

While the treatment was generally well tolerated, four out of a total 41 patients discontinued it due to side effects, the company said.

Shares of Nektar had fallen as much as 10 percent on Tuesday after the company released preliminary data that raised concerns of a fall in response rate compared with earlier data from the study.

Last February, Bristol-Myers agreed to pay Nektar $1.85 billion in a global development and profit-sharing deal for testing NKTR-214 in combination with Bristol’s immuno-oncology drugs Opdivo, and Opdivo and Yervoy in 20 cancer indications including melanoma, kidney and lung cancers.

Nektar’s NKTR-214 is designed to grow cancer killing T-cells in the body to fight the disease.

(Reporting by Manogna Maddipatla and Manas Mishra in Bengaluru; Editing by Shinjini Ganguli)

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