Micrograph showing

follicular lymphoma

LUGANO—An anti-CD37 antibody-radionuclide conjugate provides sustained efficacy and a manageable safety profile in patients with relapsed, CD37⁺ non-Hodgkin lymphoma (NHL), according to researchers.

The drug, ¹⁷⁷Lu-DOTA-HH1 (Betalutin), consists of the tumor-specific antibody HH1, which targets the CD37 antigen on the surface of NHL cells, conjugated to the β-emitting isotope lutetium-177 (Lu-177) via the chemical linker DOTA.

In an ongoing, phase 1/2 trial, Betalutin has produced responses in 7 of 12 evaluable patients with relapsed NHL, and 5 of those responses are ongoing.

Grade 3/4 adverse events (AEs) were largely hematologic in nature, and many were transient and reversible. However, grade 3/4 AEs occurred at all 3 dose levels investigated in this study, as did serious AEs.

Arne Kolstad, MD, PhD, of Oslo University Hospital in Norway, and his colleagues reported these results at the 13th International Conference on Malignant Lymphoma (abstract 287*). The study was sponsored by Nordic Nanovector, the company developing Betalutin.

Thus far, the researchers have evaluated 13 patients with relapsed, CD37⁺ NHL. Twelve patients had a primary diagnosis of follicular lymphoma, and 1 had mantle cell lymphoma (MCL). The patients’ median age was 68 (range, 41-78), and they had received 1 to 8 prior treatments.

In this dose-finding study, the researchers investigated 3 dose levels of Betalutin. Four patients received Betalutin at 10 MBq/kg biweekly, 6 received 15 MBq/kg biweekly, and 3 (including the MCL patient) received 20 MBq/kg biweekly.

All patients received 50 mg of HH1 prior to Betalutin. Patients also received rituximab at 375 mg/m² on days -28 and -21 (prior to Betalutin on day 0).

Safety and dosing

Dose-limiting toxicities occurred at the 20 MBq/kg biweekly dose, so researchers said 15 MBq/kg biweekly, with HH1 pre-dosing, is the current recommended dose of Betalutin.

Treatment-emergent grade 3 AEs in the 10 MBq/kg group included thrombocytopenia (n=1), neutropenia (n=2), pneumonia (n=1), and pulmonary embolism (n=1). There were no grade 4 AEs in this group.

In the 15 MBq/kg group, 2 patients had grade 3 thrombocytopenia, and 1 had grade 4. One patient each had grade 3 and 4 neutropenia.

Grade 3/4 AEs in the 20 MBq/kg group included grade 4 thrombocytopenia (n=3), grade 3 (n=1) and grade 4 (n=2) neutropenia, and grade 3 epistaxis (n=1).

Serious AEs included pulmonary embolism (1 in the 10 MBq/kg group), pneumonia (1 in the 10 MBq/kg group), atrial fibrillation (2 in the 15 MBq/kg group), thrombocytopenia (1 in the 20 MBq/kg group), and epistaxis (1 in the 20 MBq/kg group).

The researchers said all hematologic AEs were transient and reversible. They also pointed out that 6 patients in this trial have been followed for a year or more, and there have been no secondary malignancies or other events that would suggest long-term toxicity.

Efficacy and next steps

Twelve patients were evaluable for efficacy. Seven patients responded to treatment, including 4 complete responses (CRs) and 3 partial responses. Two patients had stable disease, and 3 progressed. Eight patients had a 50% or greater reduction in tumor volume.

The median response duration has not been reached, and 5 patients’ responses are ongoing. The duration of response in these patients ranges from 6 months to more than 21 months. All 4 patients who achieved a CR (including the MCL patient) are still in CR.

The researchers concluded that Betalutin delivers a highly favorable response rate, with durable clinical responses, and the drug has a predictable and manageable safety profile.

They have opened a new arm of this study to evaluate the safety and efficacy of Betalutin at 15 MBq/kg biweekly and 17.5 MBq/kg biweekly without HH1 pre-dosing.

*Information in the abstract differs from that presented at the meeting.

Targeted agent shows early promise for NHL