NEW YORK (TheStreet) -- Nektar Therapeutics (NKTR - Get Report) shares are falling sharply today, down 13.52% to $12.16, on heavy volume after the company announced that its breast cancer treatment candidate, NKTR-102 (etirinotecan pegol), failed to achieve statistically significant median overall survival rates.

The treatment was measured on 852 breast cancer patients who were heavily pre-treated with a median of three prior therapies for metastatic disease. NKTR-102 treated patients saw a median 2.1 month improvement in median overall survival over patients treated with only a single chemotherapy agent of physician's choice.

However, the hazard ratio for survival in the NTKR-102 group compared to the active control group was 0.87, which is determined to not be statistically significant.

"In BEACON, NKTR-102 provided a clinically meaningful benefit with a greater than two month survival advantage in these late-stage breast cancer patients, many who were refractory to existing therapies. NKTR-102 exhibited a lower rate of high grade adverse events including a reduced rate of neutropenia as compared to active control, which dramatically decreased the need for growth factor support in the NKTR-102 arm of the study," said a company spokesman.

TheStreet Ratings team rates NEKTAR THERAPEUTICS as a Sell with a ratings score of D. TheStreet Ratings Team has this to say about their recommendation:

"We rate NEKTAR THERAPEUTICS (NKTR) a SELL. This is driven by a few notable weaknesses, which we believe should have a greater impact than any strengths, and could make it more difficult for investors to achieve positive results compared to most of the stocks we cover. The company's weaknesses can be seen in multiple areas, such as its weak operating cash flow and generally high debt management risk."

Highlights from the analysis by TheStreet Ratings Team goes as follows:

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