FDA Green Lights Pfizer Drug for Rare, Fast-Killing Type of Leukemia

FDA Green Lights Pfizer Drug for Rare, Fast-Killing Type of Leukemia August 18, 2017
By Alex Keown, BioSpace.com Breaking News Staff

SILVER SPRING, Md. – Pfizer’s newly approved leukemia drug Besponsa (inotuzumab ozogamicin) will come with a black box warning over concerns of liver toxicity.

On Thursday, the U.S. Food and Drug Administration gave the nod to Besponsa for the treatment of adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL). B-cell precursor ALL is a rapidly progressing type of cancer in which the bone marrow makes too many B-cell lymphocytes, an immature type of white blood cell. The National Cancer Institute estimates that approximately 5,970 people in the United States will be diagnosed with ALL this year and approximately 1,440 will die from the disease, the FDA said in its announcement.

Richard Pazdur, director of the FDA’s Oncology Center of Excellence, said life expectancy of these B-Cell ALL patients is typically low. Patients have few treatments available and approval of Besponsa “provides a new, targeted treatment option." If left untreated B-Cell ALL can be fatal within a matter of months, Liz Barrett, global president of Pfizer Oncology said in a statement.

“Besponsa will help address a significant need for new treatment options in B-cell acute lymphoblastic leukemia, and may help more patients reach stem cell transplant, which provides the best chance for long term remission. We’re proud to build on our continued commitment to patients with hematologic malignancies, and will continue our work to find new treatments in acute lymphoblastic leukemia and other blood cancers,” Barrett said.

Besponsa is an antibody-drug conjugate (ADC) composed of a monoclonal antibody (mAb) targeting CD22, a cell surface antigen expressed on cancer cells in almost all B-ALL patients, linked to a cytotoxic agent. By doing so, Besponsa blocks the growth of cancerous cells. Besponsa was approved in the European Union earlier this year.

In Phase III trials Besponsa demonstrated efficacy in including rates of hematologic remission, MRD-negativity and stem cell transplantation, Pfizer said. In the Phase III trial, 35 percent of patients who took Besponsa experienced complete remission for a median period of eight months, compared to the 17.4 percent of patients who received alternative chemotherapy. Those patients experienced complete remission for a median of 4.9 months, Pfizer said. Considering how quickly B-Cell ALL can kill, that median of eight months is important to patients.

Hagop M. Kantarjian, lead investigator of the trial and professor at The University of Texas MD Anderson Cancer Center, said he looks forward to “seeing the impact” Besponsa will have on his patients.

Despite that efficacy, some patients did experience side effects such as low levels of white and red blood cells as well as liver toxicity issues. The FDA’s boxed warning raises concerns over hepatotoxicity of the liver, including blockage of veins in the liver (veno-occlusive disease [VOD] or sinusoidal obstruction syndrome). The boxed warning also includes an increased risk of death for patients who take Besponsa after receiving a certain type of stem cell transplant.

Additionally, the FDA said other serious side effects of Besponsa include a decrease in blood cell and platelet production, infusion-related reactions and problems with the heart's electrical pulses (QT interval prolongation).

When Pfizer begins to commercialize Besponsa in the United States, it will likely have a pre-insurance, discount and rewards price of about $168,300, Reuters said.

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