By Sriparna Roy

Dec 6 (Reuters) - Regeneron REGN.O said on Saturday its experimental cancer combination therapy was effective and showed disappearance of the disease in previously untreated patients with a type of blood cancer in the first part of a late-stage trial.

The trial, which enrolled 22 patients, studied safety and preliminary efficacy of the company's therapy, odronextamab, in combination with chemotherapy in patients with Diffuse Large B-Cell Lymphoma or DLBCL.

Odronextamab belongs to a class of treatments called bispecific antibodies that are designed to attach to a cancer cell and an immune cell, bringing them together so that the body's immune system can kill the cancer.

At the 160 mg dose of the combination, patients showed 100% complete response rate, the company said.

DLBCL is a fast-growing blood cancer that affects the lymphatic system, which is a network of tissues, vessels and organs that help fight infection in the body. It involves changes in the B cells, a particular type of white blood cell.

B-cell counts were cleared completely after the first dose of the therapy, the company said in a presentation at the American Society of Hematology Annual Meeting.

Most patients completed six cycles of the combination at both 80 mg and 160 mg dose levels. The higher dose has been selected for further studies.

Data also suggested that when combining odronextamab with the chemotherapy regimen known as CHOP, deep and lasting responses were achieved without the need for rituximab.

"Part of our focus here at Regeneron is to develop bispecifics which are extremely potent and which don't require a very heavy burdensome additional cocktail of drugs to be combined with because their activity in itself is very potent," said Aafia Chaudhry, global program head.

The company will be initiating enrollment of patients for the second part of the study to see how effective the combination is in comparison with the combination of rituximab and chemotherapy, the current standard of care treatment approved for DLBCL.

"Our strategy is to replace rituximab rather than to add on to rituximab," Chaudhry added.

(Reporting by Sriparna Roy in Bengaluru; Editing by Maju Samuel)

((Sriparna.Roy@thomsonreuters.com;))