Arcellx stock reversed lower Monday despite positive results for its rival to Legend Biotech's multiple myeloma treatment, Carvykti.
On Sunday, Arcellx said 97% of patients responded to treatment with its CAR-T drug, anito-cel, up from 95% in its prior data cut.
Across 86 patients that could be evaluated, 62% had complete responses — meaning all evidence of their cancer disappeared. And 93% of patients lived for six months before their cancer worsened. By a year, that number was 79%.
Leerink Partners analyst Daina Graybosch called the results a "best-case efficacy scenario."
She also noted that Arcellx's Gilead Sciences-partnered anito-cel could be safer than Legend's Carvykti, developed in partnership with Johnson & Johnson. There were no cases of Parkinsonism among anito-cel recipients. Parkinsonism refers to a group of neurological movement problems. It cropped up in a single-digit percentage of Carvykti patients in Legend's clinical studies.
Arcellx stock reversed lower, falling 1.9% to close at 82.95. That pulled back from a premarket gain of nearly 9%. Legend stock, on the other hand, rose a fraction, closing at 41.63.
Arcellx Stock: Rivaling Legend's Carvykti
The companies are bitter rivals in the multiple myeloma space. Over the weekend, Arcellx released the updated results from its anito-cel test at the same time Legend held an analyst meeting to discuss real-world use of Carvykti.
It's anyone's guess who will lead the space in the coming years.
Part of the problem stems from the differences in Arcellx's and Legend's studies. Legend seemingly enrolled sicker patients with Arcellx, analysts said. But Arcellx's CAR-T drug looks safer.
"We expect debates on patient selection and delayed neurotoxicity events are likely to take years to resolve," Leerink's Graybosch said in a client note.
The investment bank has an outperform rating on Arcellx stock.
Real-World Use Of Carvykti
During the Legend event, two doctors discussed real-world use of Carvykti.
Only one patient out of the roughly 200 they've treated with Carvykti has experienced Parkinsonism.
Management of cytokine release syndrome, or CRS, is also improving in the commercial world. CRS is an inflammatory condition that occurs when the immune system becomes overactive. CAR-T drugs involve stoking the immune system and, so, commonly cause CRS.
In Arcellx's study, CRS occurred in 83% of patients. Just 2% had serious events. That topped the 95% and 4%, respectively, in Legend's Carvykti studies. But, in the real world, academic centers and aligning on how to treat CRS, RBC Capital Markets analyst Leonid Timashev said in a report.
Timashev ultimately expects Carvykti to reach a peak $10 billion in sales. He expects $2 billion in sales next year, above Legend Biotech's own guidance for $1.9 billion.
He kept his outperform rating on Legend stock, but didn't list a rating for Arcellx stock.
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