Drugmaker Pfizer Inc. has halted a late-stage study of an experimental cancer compound being tested in patients with a certain form of non-Hodgkin's lymphoma, because an interim analysis showed the drug wasn't helping patients live longer.
Pfizer said late Monday that it was stopping the study of its compound, inotuzumab ozogamicin, in patients who had relapsed after or not been helped by other treatments but who were not candidates for high-dose chemotherapy.
The patients in the study all had an aggressive form of non-Hodgkin's lymphoma in which cancerous white blood cells called B-cells had a substance on their surface called CD22. That substance is found in about 90 percent of cancers involving B-cells.
Inotuzumab ozogamicin combines a cell-killing agent with an antibody attracted to CD22. By binding to CD22, the compound can enter the B-cell. Once inside, the compound then releases the cell-killing agent, called calicheamicin, to destroy the cancerous B-cell.
In the study, half of the participants were given inotuzumab ozogamicin once a month, along with a standard cancer medicine, rituximab. The other half of patients were treated with rituximab and either of two other cancer drugs.
A planned analysis of results part way through the study showed patients getting rituximab and the experimental compound were not surviving any longer than the other patients.
Pfizer said the data did not turn up any new or unexpected safety problems with the experimental compound.
The New York-based company said it is continuing another late-stage study of the compound in adults who have relapsed after or haven't responded to treatment for a type of blood cancer called acute lymphoblastic leukemia.
"We are working to better understand the findings from this review to determine if there are any patterns of outcome that may help us gain greater understanding of the potential effect of inotuzumab ozogamicin in specific patient populations," Dr. Mace Rothenberg, head of clinical development and medical affairs for Pfizer's cancer business, said in a statement.
Rothenberg noted there are more than 70 types of cancers of the lymph system, blood and bone marrow that require unique treatments. He said Pfizer is committed to evaluating inotuzumab ozogamicin in patients with those cancers.
Cancer treatments are one of the priority research areas for Pfizer, the world's second-biggest drugmaker by revenue.
Last year, the company won approval for two targeted cancer drugs, Bosulif for advanced kidney cancer and Inlyta for certain patients with chronic myelogenous leukemia. It already sold Sutent, a blockbuster that treats multiple types of cancer.