Oncternal Therapeutics’ ongoing Phase I/II Cirmtuzumab and Ibrutinib targeting ROR1 for Leukemia and Lymphoma (CIRLL) clinical trial of cirmtuzumab has demonstrated a positive effect in relapsed/refractory mantle cell lymphoma (MCL).

During the ongoing CIRLL clinical trial (CIRM-0001), the company’s lead candidate cirmtuzumab, combined with ibrutinib, showed encouraging results in a subset of participants with MCL.

The trial is evaluating cirmtuzumab in combination with ibrutinib in separate groups of patients with chronic lymphocytic leukemia (CLL) or MCL.

It completed enrollment of the dose-finding cohorts in CLL and MCL and the dose-expansion cohort in CLL.

Enrollment of the dose-expansion cohort in MCL and randomised Phase II cohort in CLL is currently underway.

Cirmtuzumab is an investigational, monoclonal antibody that targets Receptor tyrosine kinase-like Orphan Receptor 1 (ROR1).

The drug is currently in the clinical development stage. It has not been approved by the US Food and Drug Administration (FDA) for any indication.

In the dose-finding cohort of the ongoing Phase I/II clinical trial, 50% of evaluable patients with relapsed/refractory MCL achieved complete responses (CR). The trial also reported an 83% best objective response rate (ORR) and a 100% clinical benefit rate.

CIRLL clinical trial investigator Hun Ju Lee said: “The reported complete response rate for patients with MCL treated with cirmtuzumab and ibrutinib is highly encouraging and is higher than previously reported for ibrutinib alone, particularly considering that some of these patients were heavily pre-treated.

“Patients with relapsed MCL remain in dire need of well-tolerated treatment options that provide deeper and more durable responses.”

The company noted that the adverse events in the trial were consistent with those reported for ibrutinib alone.

No dose-limiting toxicities, serious adverse events attributed to cirmtuzumab alone, or discontinuations were reported in the trial.

The CIRLL clinical trial, which is being conducted in collaboration with the University of California San Diego, is supported by a grant from the California Institute for Regenerative Medicine.