AstraZeneca moves deeper into rare diseases, spending $150M on late-phase hematology prospect

AstraZeneca is continuing to build out its rare disease pipeline, pulling the trigger on an option to buy Caelum Biosciences that it picked up in its takeover of Alexion. The buyout gives AstraZeneca control of a phase 3 treatment for the rare hematology disease light chain (AL) amyloidosis.

Alexion secured the right to acquire Caelum early in 2019 as part of a deal that saw it pay $30 million for a 19.9% stake in the biotech. The deal positioned Alexion to make a decision after getting a look at midphase data on a monoclonal antibody designed to take out the amyloid deposits that build up around tissues in AL amyloidosis patients and cause progressive organ damage.

Having bought Alexion for $39 billion, AstraZeneca had until January 2022 to decide whether to pay a far smaller sum to acquire Caelum. AstraZeneca ultimately made the decision months ahead of the deadline.

The takeover sees AstraZeneca pay $150 million and commit up to $350 million in milestones to add Caelum’s CAEL-101 to its rare disease pipeline. Caelum moved CAEL-101 into a pair of phase 3 trials last year on the strength of a midphase program that supported safety and tolerability and a phase 1 trial that provided evidence of the long-term effects of the drug on cardiac function. 

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Overall survival of AL amyloidosis patients has improved in recent decades, but many patients still die in the months and years after diagnosis, often from cardiac failure. In Caelum’s phase 1a/1b clinical trial, 78% of participants were alive at 37 months. Caelum later studied higher doses in phase 2 and selected one of them for the pivotal program.

CAEL-101 is closing in on pivotal data at a time of change in the AL amyloidosis market, with the approval of Johnson & Johnson’s Darzalex giving patients a new treatment option. In combination with Takeda’s Velcade, Darzalex is now emerging as a novel standard of care. 

Caelum responded by adding an additional phase 2 study arm that showed the safety of CAEL-101 in combination with a Darzalex-based regimen. The phase 3 studies, which have primary completion dates in August 2022, are using the cyclophosphamide, bortezomib and dexamethasone regimen as the control.