(PFE) - Get Report

said it will stop developing two drug candidates in the company's pipeline, one for treating HIV and AIDS and another for chronic obstructive pulmonary disease and asthma.

In a press release Friday, the drug giant said it's ending the development of capravirine, a non-nucleoside reverse transcriptase inhibitor under study for patients with HIV or AIDS who haven't been helped by available antiretroviral therapies.

Pfizer based the decision on the results of two Phase IIb studies that failed to show a statistically significant difference between standard triple-drug HIV therapies and the same therapy combined with capravirine. Rights to the compound will be returned to

Shionogi & Co.

Additionally, Pfizer and



agreed to terminate their collaboration involving the development of Daxas, a treatment for chronic obstructive pulmonary disease and asthma. Pfizer is returning all rights to the product candidate to Altana.

"The search for new and innovative medicines for the treatment of HIV/AIDS, COPD and asthma remains a priority for Pfizer and we will continue to invest in other research activities in these areas to address the needs of patients and health care providers," the company said.

Shares of Pfizer were down 8 cents to $27.50 in premarket trading.