Shares in German biopharma Affimed dropped near 30% after the company said it was placing a key Phase I programme of its experimental cancer immunotherapy on hold because of serious side effects observed in trials, including a patient death.

AFM11 (CD19/CD3-targeting T cell engager) is currently being assessed in two Phase I clinical studies for the treatment of patients with relapsed or refractory CD19 positive B-cell non-Hodgkin lymphoma (NHL) and acute lymphoblastic leukemia (ALL).

However, serious adverse events (SAEs) were observed in three patients, including a death in the ALL study and two life-threatening events in the NHL study, causing the company to suspend clinical activity on the drug.

The SAEs occurred in people taking the highest doses of the drug in each study, the firm said, also noting that 33 patients have now been treated with AFM11 in the trials, “with preliminary signs of clinical activity observed in several patients”.

Affimed said it would no work closely with global health authorities, safety monitoring committees, and clinical investigators to carefully assess the data and determine next steps for the AFM11 programme.