Cellectis S.A. (NASDAQ: CLLS) shares tumbled early on Tuesday after the firm announced that a couple of its early-stage studies in acute myeloid leukemia (AML) and blastic plasmacytoid dendritic cell neoplasm (BPDCN) were put on hold. Specifically, the U.S. Food and Drug Administration (FDA) placed a clinical hold on both UCART123 Phase 1 studies.
The clinical hold was initiated after Cellectis reported one fatality in the BPDCN clinical trial (ABC study). This was the first patient treated in the BPDCN study, a 78-year-old male treated with one prior therapy, who presented with relapsed/refractory BPDCN with 30% blasts in his bone marrow and cutaneous lesions (biopsy-proven BPDCN) at baseline prior to conditioning regimen.
On August 16, 2017 (Day 0), the patient received the first dose level explored in the protocol, without complication. At Day 5, the patient experienced a grade 2 cytokine release syndrome (CRS), and a grade 3 lung infection, which quickly improved after a first dose of tocilizumab and institution of anti-infective therapy (broad spectrum intravenous antibiotics). He then experienced at Day 8 a grade 5 CRS, together with a grade 4 Capillary Leak Syndrome. Despite a treatment in keeping with CRS management including administration of corticosteroids and tociluzumab x 2 as well as intensive care unit support, the patient died on Day 9.
The first patient treated in the AML study was a 58-year-old woman, with 84% blasts in her bone marrow at baseline prior to conditioning regimen. On June 27, 2017 (Day 0), the patient received the same preconditioning regimen and the same dose of UCART123 as the BPDCN patient, without complication.
The AML patient experienced an initial grade 2 CRS at Day 8, worsening to a grade 3 at Day 9 and resolving at Day 11 with treatment management in intensive care unit. She also experienced a grade 4 capillary leak syndrome at Day 9, resolved at Day 12.
Shares of Cellectis were last seen down 23% at $24.74, with a consensus analyst price target of $41.50 and a 52-week range of $16.09 to $32.46.