ADC Therapeutics Stock Is Plunging Today - What's Going On?

ADC Therapeutics SA ADCT has voluntarily paused enrollment of new patients in the Phase 2 LOTIS-9 trial evaluating Zynlonta (loncastuximab tesirine-lpyl) and rituximab (Lonca-R) in unfit or frail patients with previously untreated diffuse large B-cell lymphoma.

The move comes after a recent review of aggregate data of the 40 patients enrolled in the trial and consultation with the Data Monitoring Committee, which signaled potentially excessive respiratory-related events. 

These respiratory-related treatment-emergent adverse events (TEAEs) included seven Grade 5 fatal events and five Grade 3 or Grade 4 respiratory-related TEAEs. 

As per the investigator's assessment, eleven of the twelve events (including six of the seven Grade 5 fatal events) were individually assessed as unlikely or unrelated to the study drug. 

Four of the five Grade 3 or Grade 4 events have since been resolved, and the patients have completed treatment per protocol. 

The cause of these events remains under further investigation.

All patients with fatal events had one or more significant active underlying respiratory and/or cardiac co-morbidities

The company's decision to pause enrollment enables time to evaluate data around the TEAEs and determine the next steps. 

The company does not expect to report additional data from the trial by the end of the year.

In June, ADC Therapeutics shared updated results from the Phase 2 LOTIS-2 trial of Zynlonta in patients with relapsed/refractory diffuse large B-cell lymphoma at the European Hematology Association.

The data showed Zynlonta in patients with relapsed or refractory DLBCL after ≥2 prior systemic therapies resulted in an overall response rate (ORR) of 48.3%, with a complete response (CR) rate of 24.8% (36/145). The median (range) time to response was 41.0 (35 to 247) days for all responders and 42.0 (36 to 247) days for patients with a CR. 

Price Action: ADCT shares are down 15.60% at $2.00 during the premarket session on the last check Tuesday.