Bluebird has a promising new update on its BCMA CAR-T for multiple myeloma, but is it still the leader?

Nick Leschly / Boston Globe, Endpoints News

Bluebird bio $BLUE unveiled its latest update on its closely-watched BCMA-targeting CAR-T for multiple myeloma today offering a slate of solid evidence that demonstrates the promise that attracted Celgene $CELG to their ambitious collaboration on this drug. But with a rival Chinese group making a splash at ASCO this year, the biotech may be seeing its status as the frontrunner in the field start to fade a bit.

In the first new data to come out since late last year, bluebird offered an update on 18 patients in four different dosing cohorts in search of insights on durability, dosing and safety for bb2121.

With 18 patients evaluable for efficacy, there were 15 in what bluebird termed active dosing regimens above the minimum for bb2121, and all of them achieved an objective response. Twelve achieved a very good partial response to complete response, associated with longer survival times. And of the 4 patients evaluable for minimal residual disease status, all were MRD negative with only a few or no myeloma cells in circulation.

That is all excellent.

Up until now, bluebird and Celgene were widely viewed as the leaders in the BCMA field. But Nanjing Legend’s data out this morning may well put that status in question.

I asked bluebird CEO Nick Leschly about that over the weekend.

His response, with a smile: “We are completely, constructively paranoid no matter what.”

Short translation: Bluebird is happy where they are and confident about moving to next steps as their partner Celgene lays the foundation for a groundbreaking registrational study that may well get started later this year. But they all know it won’t be easy or free of challenges — now or in the future as rival therapies line up to challenge them.

Data from trials that don’t involve head-to-head designs within the construct of the same study are notoriously difficult to compare. In Legend’s case, says Leschly, it seems evident that the patients weren’t as sick and hadn’t failed the same multiple of drugs that bluebird recruited for.

That makes it “apples and oranges,” he says, adding “that doesn’t mean it isn’t great data.”

All of it, notes Leschly, helps validate the target, while bluebird is satisfied that it has the right drug to take forward. Its next-gen drug, bb21217, will come up behind it as Celgene preps for the pivotal BCMA study to some. “It’s all go, go, go” on bb2121, says Leschly, whose official title is chief bluebird.

“All these patients are doing incredibly well,” says the CEO about his lead therapy, pointing to partial responses in their study that reflected a near erasure of cancer. These drugs face a high bar on demonstrating efficacy, he adds, and bb2121 comes through with flying colors.

Bluebird came to ASCO with a few things to prove. It needed to prove that its drug works in a broader number of patients. And it needed to prove that the safety issues around cytokine release syndrome were manageable.

Bluebird’s CEO is coming out of ASCO believing that he’s answered those challenges.

I asked Leschly about the debate over the 4-1BB costimulatory domain its drug uses, and the theory that it could be safer than the CD28 alternatives on the market.

Leschly’s remark: he’s learned to “be careful of opening your mouth before you know what you’re talking about.”

The 4-1BB domain does seem to help durability, he adds, but he’s hesitant to say that it extends to safety at this point. It’s just too early.

Bluebird’s execs say they still have to decide exactly which dose to take into the next phase of their study (and I pressed them on it), as they add new patients and prepare for the pivotal study to come.

Celgene is clear that they want to start enrolling for the pivotal study this year, says Leschly. And with 50% of the US commercial rights residing at bluebird, he’s ready for the next step.

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