The goal of many cancer researchers is to find effective treatments that have few adverse effects.

Researchers at Fox Chase Cancer Center in Philadelphia in collaboration with co-investigators at other centres and Merck Inc. are one step closer to finding such a treatment for urothelial cancer, for which chemotherapy is currently the standard of care.

The anti–PD-1 antibody pembrolizumab demonstrated antitumour activity with little toxicity in a group of 33 patients with recurrent or metastatic PD-L1–positive urothelial cancer, the researchers found.

Elizabeth Plimack, MD, MS, director of genitourinary clinical research and associate professor of medical oncology at Fox Chase, presented data from the study at the 2015 American Society of Clinical Oncology Annual Meeting.

Pembrolizumab is currently FDA-approved to treat patients with metastatic melanoma.

It is a type of immunotherapy that works by releasing the body’s own immune system to target and attack cancer cells.

Chemotherapy, in contrast, works by killing cancer cells.

However, it can also kill healthy, non-cancer cells, which leads to the well-known adverse effects.

“PD-L1 is a protein expressed by cancer cells that interacts with receptors on T cells, telling them to back off,” Plimack said.

“Pembrolizumab targets the receptors on the T cells and prevents the interaction, allowing the immune system to attack the cancer.”

According to Plimack, approximately 4.5 percent of all new cancer cases each year are urothelial cancers.

The most common type is bladder cancer, but urothelial cancer also affects the ureters and the urethra.

In this study, approximately 64 percent of patients with urothelial cancer expressed PD-L1.

The data Plimack presented are from the phase Ib KEYNOTE-012 study.

The 33 patients received pembrolizumab every 2 weeks until they either had a complete response, cancer progression, or experienced unacceptable adverse effects.

The patients were followed for a median of 13 months.

During that time, the response rate was 27.6 percent; more than one-quarter of the patients enrolled responded to the treatment.

Only five patients experienced serious drug-related adverse effects.

“Pembrolizumab is a drug that helps the patients’ own immune system fight cancer,” Plimack said.

“It’s a novel therapeutic approach, and a group of patients on this study appeared to have durable responses to it.”

A phase III trial is underway, where the drug will continue to be evaluated for safety and efficacy in comparison to chemotherapy within a larger group of patients.

Source: ASCO