Nektar Therapeutics Pharmaceutical company

Shares of drugmaker Nektar Therapeutics (NKTR - Get Report)  were dropping nearly 40% Friday after the company announced manufacturing issues in two batches of experimental cancer drugs that the company gave to patients in a trial. 

Those two batches resulted in treatment responses that weren't as optimistic as expected, leading analysts at J.P. Morgan, Jefferies and Mizuho Securities to downgrade the stock to hold. 

Separately, the company reported a quarterly loss of 63 cents a share on revenue of $23.3 million. Analysts were expecting a loss of 80 cents q share on revenue of $26.6 million. 

"Nektar is making good progress advancing our multiple programs in immuno-oncology, immunology and pain," said Howard W. Robin, president and CEO of Nektar. "With our partner Bristol-Myers Squibb, although we've experienced some delays, we are working to finalize the development program for bempegaldesleukin in combination with nivolumab in a number of tumor types and which are designed to support registration for this unique I-O doublet."