While much of the focus at this year's American Society of Clinical Oncologists meeting will be focused on immuno-oncology partnerships between the so called "checkpoint inhibitors" and targeted cancer therapies, several companies are taking the next step. Amgen (NASDAQ:AMGN)has plans to present data from its unique bispecific antibody blinatumomab at ASCO, and AstraZeneca (NASDAQ:AZN)and Roche (OTC:RHHBY) are among other companies with bispecifics in the works.
What good is a bispecific antibody?
Immuno-oncology has been approached from two different angles. First, there's the cancer vaccine. In order to harness the power of the immune system to fight cancer cells, T-cells must recognize a tumor as being foreign. Cancer vaccines train the immune system to identify markers on the surface of tumor cells, to encourage the body's natural defenses to gobble them up. Cancer vaccines have been notoriously difficult to develop and the only FDA approved vaccine, Provenge from Dendreon, has had little commercial success.
Then there's the checkpoint inhibitors. Checkpoint inhibitors, like the PD-1 inhibitors taking the industry by storm, act by removing built-in brakes on the immune system to boost the response to tumor cells. So far Bristol-Myers Squibb's nivolumab and Merck's MK3475 stand out as the leaders in the group.
By linking antibody fragments that recognize tumor antigens and a T-cell surface marker, it may be possible to harness the benefits of both approaches into a single multi-purpose molecule. That molecule would ideally activate a killer T-cell, and in the process recruit that activated cell to the tumor with its cancer-specific portion.
Who are the players?
When Amgen acquired Micromet in 2012, it picked up a BiTE, or bispecific T-cell engager with potential in fighting B-cell lymphomas and leukemias. Blinatumomab combines features of both cancer vaccines and checkpoint inhibitors by linking antibodies against the CD19 marker for B-cells with antibodies against the T-cell activator CD3. On Tuesday Amgen will present data from a pivotal Phase 2 study of blinatumomab in relapsed/refractory B-precursor acute lymphoblastic leukemia, or ALL, in which B-cells of the immune system have grown rampant.
Blinatumomab, which has received orphan drug designation from the FDA, showed a 43% complete response rate in the confirmatory open label study. According to the American Cancer Society, nearly half of the 80% of patients that achieve remission have a relapse, so a large unmet medical need exists for patients facing the disease for a second time. But while the bispecific immunotherapy appears to be an emerging option for ALL patients, it isn't alone. Ibrutinib, marketed as Imbruvika by Pharmacyclics and Johnson & Johnson, is also in a phase 2 trial to treat ALL.
AstraZeneca and Roche's Genentech have also joined the bispecific antibody party, having both struck deals with privately owned Immunocore for its CD3 ImmTAC bispecific antibodies. The two companies find themselves grabbing more of the immuno-oncology spotlight with impressive data at ASCO, and would do well to channel that momentum into Immunocore's innovative approach. AstraZeneca, having successfully rebuffed takeover bids by Pfizer, must now prove to investors that its worthy of operating as an independent Big Pharma player. That will mean circling the wagons around its until recently under-appreciated oncology pipeline.
For Roche the focus for now is on its checkpoint inhibitor MPDL3280A, and on leveraging its massive pipeline to quietly initiate combination studies with its own targeted drugs. Genentech's respected history of innovation, combined with Immunocore's technology, could provide drug candidates to fill the back end of the pipeline as more mature therapies advance through trials.
The bottom line
It's never too early to ask where the next spark of innovation will come from. With the success of checkpoint inhibitors thus far, and just a touch of innovation, it's possible that bispecific antibodies could solve the problem that cancer vaccines have yet to effectively address. Keep an eye on these players and others as bispecific antibodies gain more traction.