ADC Therapeutics Blood Cancer Drug Trial Shows More Deaths Despite Meeting Primary Endpoint

ADC Therapeutics' late-stage trial of Zynlonta combined with Roche's Rituxan in relapsed or refractory diffuse large B-cell lymphoma met its primary progression-free survival endpoint but showed 27 deaths (13.2%) in the treatment arm versus 9 deaths (4.6%) in the control arm receiving Rituxan and chemotherapy. Shares plunged 53% on June 4, 2026. The company plans an FDA meeting in August 2026 for the drug, which received accelerated approval in 2021.

Clinical trial results

• ▪A late-stage study testing ADC Therapeutics' Zynlonta along with Roche's Rituxan in patients with relapsed or refractory diffuse large B-cell lymphoma met its main goal of improving progression-free survival.
• ▪Diffuse large B-cell lymphoma is an aggressive, fast-growing blood cancer that affects the lymphatic system.
• ▪The confirmatory study tested ADC Therapeutics' Zynlonta along with Roche's monoclonal antibody Rituxan in patients with relapsed or refractory diffuse large B-cell lymphoma.
• ▪ADC Therapeutics' Zynlonta is an antibody-drug conjugate designed to precisely target cancer cells while limiting damage to healthy tissue.

Death rate disparity

• ▪Most deaths in the ADC Therapeutics Zynlonta treatment arm occurred in patients aged 75 years or older.
• ▪ADC Therapeutics attributed the higher death rate in part to the older patient population and longer adverse event monitoring in the treatment arm, where patients stayed on therapy longer as control-arm patients often switched early to other treatments.
• ▪There were 27 deaths, or 13.2%, in the ADC Therapeutics Zynlonta treatment arm, compared with 9 deaths, or 4.6%, in the control arm that received Rituxan and chemotherapy.
• ▪Guggenheim analyst Michael Schmidt said the result was overshadowed by a higher rate of deaths in the Zynlonta arm, despite other efficacy endpoints looking favorable.

FDA approval pathway

• ▪ADC Therapeutics shares slumped nearly 53% in premarket trading on June 4, 2026.
• ▪ADC Therapeutics plans to submit a supplemental application in the fourth quarter of 2026.
• ▪The confirmatory study was crucial to show ADC Therapeutics' Zynlonta's clinical benefits for full approval in the U.S.
• ▪ADC Therapeutics plans to meet with the FDA in August 2026.
• ▪ADC Therapeutics' Zynlonta was granted an accelerated approval by the U.S. Food and Drug Administration in 2021.

Perspective of Guggenheim analyst Michael Schmidt

• ▪Guggenheim analyst Michael Schmidt said the result was overshadowed by a higher rate of deaths in the Zynlonta arm, despite other efficacy endpoints looking favorable.

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