ADC Therapeutics Posts Early Phase II Lymphoma Data for Zynlonta as Revenue Drops 5.8%

Antibody Drug Conjugate with Cytotoxic Payload

Pictured: 3D illustrations of antibody-drug conjugates carrying their toxic payloads/iStock, Love Employee

ADC Therapeutics on Monday released topline Phase II data for its anti-CD19 antibody drug conjugate Zynlonta (loncastuximab tesirine-lpyl), which elicited high rates of treatment response in patients with relapsed or refractory marginal zone lymphoma.

Monday’s early data come from 15 evaluable patients out of the total 50 enrolled participants in ADC Therapeutics’ single-arm, open-label mid-stage study. Thirteen of these patients showed complete response (CR) to Zynlonta, while one other patient demonstrated partial response. All treatment responses were maintained until the time of data cut-off.

As for safety, Zynlonta was generally well-tolerated and its adverse event profile was consistent with what had been established in prior studies. One patient dropped out of the study due to toxicities, though this “fully resolved” once Zynlonta treatment was discontinued, according to the biotech’s news release. This patient remains in CR.

With these data in hand, and as long as readouts continue to be positive, ADC Therapeutics plans to “potentially pursue a regulatory pathway and compendia in parallel,” CMO Mohamed Zaki said in a statement.

Concurrent with Monday’s readout, the biotech announced that it was putting up for sale more than 13.4 million of its common shares at $4.90 apiece. The company is offering pre-funded warrants to purchase over 8.1 million common shares at $4.812 per pre-funded warrant. In total, ADC Therapeutics is looking to make around $105 million in gross proceeds.

Zynlonta is an antibody-drug conjugate (ADC) designed to target the CD19 surface protein, which is typically found on B cells and is a well-validated target in related malignancies. Once bound to its target, Zynlonta is internalized by the cancer cell and releases its toxic pyrrolobenzodiazepine payload, which in turn targets the DNA and ultimately triggers cell death.

The ADC won the FDA’s accelerated approval in April 2021 for the treatment of patients with relapsed or refractory large B-cell lymphoma who had undergone at least two prior lines of systemic therapy. The approval also includes certain types of diffuse large B-cell lymphoma.

In July 2023, ADC Therapeutics discontinued the Phase II LOTIS-9 trial of Zynlonta in previously untreated, difficult-to-treat diffuse large B-cell lymphoma after seven patient deaths.

Sales for Zynlonta have been largely disappointing. In 2023, the ADC brought in $69.1 million, down from $75 million in 2022. The biotech also reported its first-quarter earnings on Monday, posting that Zynlonta’s sales dropped to $17.85 million from nearly $19 million during the same period in 2023.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at tristan@tristanmanalac.com or tristan.manalac@biospace.com.

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