The market for complex therapies that train living cells to attack cancer is taking baby steps, but there's still a lot of enthusiasm for experimental drugs coming through the pipeline from bluebird bio (NASDAQ: BLUE) and it's big biotech partner Celgene (NASDAQ: CELG). That enthusiasm fell a notch after Amgen (NASDAQ: AMGN) released exciting data from a handful of patients that suggests it's found a much easier way to achieve the same goal.
Investors shouldn't make buy or sell decisions based on data from a handful of people taking competing treatments. That said, there are a few things about Amgen's fancy T-cell engagers that investors need to know, starting with the eye-popping results.
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Pleasing a tough crowd
At a recent scientific conference, Amgen shared preliminary data from five patients with multiple myeloma so aggressive that their disease didn't back down after four to six previous lines of treatment. Eliciting minor responses from just a couple would be impressive, but AMG-420 went way beyond and helped five patients treated with a higher dosage achieve complete remission.
If AMG-420 pulls off a repeat performance in a larger study, bluebird bio and Celgene's partnered candidate, bb2121, might be in trouble. Investigators couldn't detect any sign of disease activity for four patients treated with a higher dose of AMG-420, and responses were still going strong for four patients at an observation point at least 10 months after beginning treatment.
We really shouldn't make apples-to-apples comparisons without a head-to-head study, but Amgen's candidate looks like a potential threat to bb2121 in terms of efficacy. For comparison, bluebird's shown us that 11 out of 22 advanced stage multiple myeloma patients treated with a higher dose of bb2121 were in complete remission at a median follow-up of 6.5 months.
A simpler mousetrap
Each patient treated with bluebird and Celgene's bb2121 had their T-cells removed, then shipped to a manufacturing site where they're trained to express a chimeric antigen receptor (CAR-T) that recognizes beta cell maturation antigen (BCMA), which is usually found on cancerous plasma cells.
Manufacturing a new batch for each patient isn't the only challenge CAR-T therapies face. Before starting CAR-T therapy, patients need to hang around a hospital for at least a few days while nurses kindly wipe out their immune systems with lymphodepleting chemotherapy.
AMG-420 is part of a drug class called bi-specific T-cell engagers (BiTEs), which are just two-sided proteins that can be taken off a shelf and plugged into a patient's IV drip. Despite being easier to manufacture, warehouse, and administer to patients, AMG-420 accomplishes the same complex task as bb2121 by clinging to BCMA with one arm, while the opposite side engages T-cells and holds them in place until they cause the cancerous cell to burst.
It's still early
Before bluebird bio and Celgene investors get bent out of shape, they should wait for follow-up AMG-420 data that Amgen will present this December at the American Society of Hematology's annual meeting. The first look at a handful of patients was encouraging, but there's still a lot that can go wrong.
Amgen's also advancing a similar candidate directed at BCMA called AMG-701, which is designed to last a lot longer in the bloodstream. It's in phase 1 testing at the moment, which means next year we could learn if it does a better job with a more convenient dosing schedule.
A move up the line?
Even if AMG-420 doesn't end up matching bb2121 on efficacy, keeping its safety profile intact could make it a popular option in earlier treatment settings. That could eventually be a problem for Celgene, which expects its second-best-selling multiple myeloma drug Pomalyst to generate $2 billion in sales this year.
Pomalyst is for patients who have already failed two lines of treatment, and it isn't easy to tolerate. During studies leading to the drug's approval, 51% of patients taking Pomalyst lost enough white blood cells to require hospitalization.
It's a bit early to worry about AMG-420 moving up to the third line setting before we've seen a full set of clinical trial data. That said, investors should know that Amgen's first BiTE, Blincyto, is easy enough to tolerate that it recently earned Food and Drug Administration approval to treat relatively healthy patients with a rare form of leukemia that's already in remission after their first or second line of treatment.
If it turns out that AMG-420 is as easy to tolerate as Blincyto and eventually earns a spot third in line or better, Celgene could experience an uphill slog trying to sell Pomalyst.
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