Pfizer cancer drug shows promise in combo with Merck's Keytruda

(Reuters) - An experimental Pfizer drug that helps the immune system fight cancer showed early promise against a variety of cancers when used with Merck & Co’s immunotherapy Keytruda in a small clinical trial, according to data released on Wednesday.

A company logo is seen at a Pfizer office in Dublin, Ireland November 24, 2015. REUTERS/Cathal McNaughton

The first wave of successful cancer immunotherapies, such as Keytruda, block mechanisms that tumors use to evade the immune system. Pfizer’s utomilumab, which targets an antibody known as 4-1BB, stimulates a more intense immune system attack. The Pfizer drug has already shown encouraging early results against a form of blood cancer when used with Roche’s Rituxan.

Researchers are hopeful that combining the two approaches, one that takes the brakes off of the immune system with one that hits the accelerator, will offer long-lasting protection against cancer without adding serious side effects.

Pfizer has been lagging the leaders in the immuno-oncology field, but has a large pipeline of such medicines and appears to be ahead in development of an agent that targets 4-1BB. It has high hopes that utomilumab can safely deliver impressive tumor-fighting activity in combinations with other medicines.

The new data will be presented next month at the American Society of Clinical Oncology meeting in Chicago. The study tested the combination of utomilumab and Keytruda in a small number of patients with advanced disease, including pancreatic cancer, colorectal cancer, kidney cancer, thyroid cancer and two major forms of lung cancer.

Among the 23 patients, 6 experienced complete or partial responses, meaning their tumors disappeared or shrank.

Complete remissions occurred in one patient with small cell lung cancer and one with kidney cancer. The first has been cancer-free for nearly a year and the latter for more than 12 months.

Researchers found no adverse drug interactions or serious liver problems from the treatment combination, and did not report additional toxicity with higher doses of the Pfizer drug.

Chris Boshoff, head of immuno-oncology for Pfizer, said the results suggest the two drugs can be safely combined and provide “early indication of anti-tumor activity across a number of solid tumors.”

He stressed that the study was far too small to declare the combination a success. But Boshoff said he was “very encouraged by the safety,” particularly since they have yet to determine a maximum tolerated dose of utomilumab.

Reporting by Bill Berkrot; Editing by Nick Zieminski