CLR 131 Significantly Reduces DLBCL Patients’ Tumor Size in Phase 2 Trial

CLR 131 Significantly Reduces DLBCL Patients’ Tumor Size in Phase 2 Trial

The investigative drug CLR 131 all but eliminated tumor cells in one-third of diffuse large B-cell lymphoma (DLBCL) patients treated in a Phase 2 trial, and is showing promise in other kinds of lymphoma, drug manufacturer Cellectar Biosciences announced.

The extent of tumor reduction ranged from 60% to more than 90% in the DLBCL patients. Among those with other types of lymphoma, a patient with advanced Waldenström macroglobulinemia had a 94% tumor reduction and a complete clearance of four of five masses.

“We are very encouraged by the strong response rates and meaningful reductions in tumor volumes seen in the trial to date in this very sick and heavily pretreated relapsed/refractory DLBCL patient population,” James Caruso, president and chief executive officer of Cellectar Biosciences, said in a news release. “We believe these data combined with the activity seen to date in other hematologic malignancies further validate the continued development of CLR 131.”

CLR 131 is a phospholipid drug conjugate (PDC), a cancer therapy that explores the tumor-targeting properties of lipid (fat) molecules to selectively deliver radiation to malignant cells. This is expected to minimize radiation exposure to normal tissue.

Cellectar’s Phase 2 trial (NCT02952508) was designed to test this approach in patients with relapsed or refractory B-cell cancers, including multiple myeloma; chronic lymphocytic leukemia/small lymphocytic lymphoma; lymphoplasmacytic lymphoma; marginal zone lymphoma; mantle cell lymphoma, and DLBCL.

DLBCL patients must have relapsed or failed to respond to chemotherapy regimens containing Rituxan (rituximab) and an anthracycline.

The study’s main objective is to determine the proportion of patients achieving at least disease stabilization — a measure called clinical benefit rate — after a single injection of CLR131 CLR 131. Patients had the possibility of receiving a second injection of equal dose 75 to 180 days later.

Other measures include the time a patient lives without the disease worsening and overall survival.

Results from the DLBCL group have shown that half of patients achieved at least disease stabilization, and a third saw a reduction in tumor burden ranging from 60% to over 90%.

Cellectar will now expand the DLBCL group to include 30 more patients.

The company has also reported promising results in a 67-year-old women with Waldenström macroglobulinemia — a kind of lymphoplasmacytic lymphoma — who had failed two prior therapies.

Fifty-two days after receiving CLR 131, the patient’s tumors had reduced by half, leading researchers to administer a second dose of the therapy.

Two months later, the patient showed a 94% reduction in one tumor, and four of her five masses were gone. Researchers continue to follow her progress.

“In addition to a robust clinical response, we were also happy to see resolution of symptoms that affected the patient’s quality of life, including shortness of breath associated with moderately sized pleural effusion [liquid surrounding the lungs] shortly after the patient’s first dose of CLR 131,” Sikander Ailawadhi, MD, an associate professor at the Mayo Clinic in Jacksonville, Florida, said in another news release.

CLR 131 has received orphan drug status by the U.S. Food and Drug Administration for the treatment of multiple myeloma.

In addition to the ongoing Phase 2 trial, the drug is being evaluated in a Phase 1 trial (NCT02278315) in patients with relapsed or refractory myeloma.

Cellectar is also launching another Phase 1 trial (NCT03478462) to test the safety and early effectiveness of increasing doses of CLR 131 in children and adolescents with advanced brain cancer, solid tumors, and lymphoma.

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