On March 11, 2020 Oncternal Therapeutics, Inc. (Nasdaq: ONCT), a clinical-stage biopharmaceutical company focused on the development of novel oncology therapies, reported an interim clinical data update for cirmtuzumab, a ROR1-targeted monoclonal antibody, combined with ibrutinib, in patients with relapsed/refractory mantle cell lymphoma (MCL) as part of the ongoing Phase 1/2 CIRLL (Cirmtuzumab and Ibrutinib targeting ROR1 for Leukemia and Lymphoma) clinical trial (data cutoff as of March 6, 2020) (Press release, Oncternal Therapeutics, MAR 11, 2020, View Source [SID1234555423]):

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50% Complete Response (CR) rate (6 of 12 evaluable patients), determined by Cheson criteria. One of the six patients had a complete metabolic response (CMR) by PET scan, with a bone marrow biopsy pending. All six CRs are ongoing, including one patient who has remained in CR at over 21 months on study. Four of the six patients achieved CRs within four months on the combination of cirmtuzumab and ibrutinib
33% Partial Response (PR) rate (4 of 12)
17% Stable Disease (SD) rate (2 of 12)
83% best Objective Response (CR or PR) rate (ORR)
100% Clinical Benefit (CR, PR or SD) rate
Median follow-up 6.4 months
Patients had received a median of two prior therapies before participating in this study including chemotherapy; autologous stem cell transplant (SCT); autologous SCT and CAR-T therapy; autologous SCT and allogeneic SCT; and ibrutinib with rituximab
The combination of cirmtuzumab plus ibrutinib has been well tolerated in this study, with adverse events consistent with those reported for ibrutinib alone. There were no dose-limiting toxicities, no discontinuations and no serious adverse events attributed to cirmtuzumab alone.

"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," said Hun Ju Lee, M.D., Associate Professor of Medicine in the Department of Lymphoma & Myeloma at the University of Texas MD Anderson Cancer Center, who is an investigator on the CIRLL clinical trial.

The CIRLL clinical trial is supported by a grant from the California Institute for Regenerative Medicine (CIRM) and is being conducted in collaboration with the University of California San Diego (UC San Diego).

"We are encouraged by the complete response rate for patients with MCL reported in the ongoing CIRLL clinical trial, and look forward to further developing cirmtuzumab in the ongoing clinical trials for patients with MCL, chronic lymphocytic leukemia (CLL) and breast cancer, as well as potentially for other ROR1-expressing solid tumors and hematological malignancies," said James Breitmeyer, M.D., Ph.D., Oncternal’s President and CEO.

About the CIRLL Clinical Trial

The CIRLL clinical trial (CIRM-0001) is a Phase 1/2 trial evaluating cirmtuzumab in combination with ibrutinib in separate groups of patients with CLL or MCL. Enrollment of the dose-finding cohorts in CLL and MCL and dose-expansion cohort in CLL has been completed. Enrollment of the dose-expansion cohort in MCL and randomized Phase 2 cohort in CLL is ongoing. Based on the data from the dose-finding cohorts, the recommended dosing regimen was determined to be 600 mg of cirmtuzumab administered intravenously every two weeks for three doses, followed by dosing every four weeks, in combination with 420 mg of ibrutinib administered once daily for patients with CLL, or 560 mg of ibrutinib once daily for patients with MCL, which are the FDA-approved doses of ibrutinib in these indications. Additional information about the CIRM-0001 clinical trial and other clinical trials of cirmtuzumab may be accessed at ClinicalTrials.gov.

About Cirmtuzumab

Cirmtuzumab is an investigational, potentially first-in-class monoclonal antibody targeting ROR1, or Receptor tyrosine kinase-like Orphan Receptor 1. Cirmtuzumab is currently being evaluated in a Phase 1/2 clinical trial in combination with ibrutinib for the treatment of CLL or MCL, in a collaboration with the UC San Diego School of Medicine and the California Institute for Regenerative Medicine (CIRM). In addition, an investigator-initiated Phase 1 clinical trial of cirmtuzumab in combination with paclitaxel for women with metastatic breast cancer is being conducted at the UC San Diego School of Medicine.

ROR1 is a potentially attractive target for cancer therapy because it is an onco-embryonic antigen – not usually expressed on adult cells, and its expression confers a survival and fitness advantage when reactivated and expressed by tumor cells. Researchers at the UC San Diego School of Medicine discovered that targeting a critical epitope on ROR1 was key to specifically targeting ROR1 expressing tumors. This led to the development of cirmtuzumab, that binds this critical epitope of ROR1, which is highly expressed on many different cancers but not on normal tissues. Preclinical data showed that when cirmtuzumab bound to ROR1, it blocked Wnt5a signaling, inhibited tumor cell proliferation, migration and survival, and induced differentiation of the tumor cells. Cirmtuzumab is in clinical development and has not been approved by the U.S. Food and Drug Administration for any indication.