Novel Radiotherapeutic Granted FDA's Fast Track Designation for R/R Multiple Myeloma

Novel radiotherapeutic CLR 131 has been granted a fast track designation from the FDA as a fourth-line or later treatment for patients with relapsed or refractory multiple myeloma.¹

The agent is being evaluated in phase I and II trials in adult and pediatric patients with various solid tumors and B-cell hematologic malignancies, including in the ongoing multicenter phase II CLOVER-1 trial (NCT02952508).

“Fast Track Designation furthers our efforts to expeditiously develop CLR 131 as a new, innovative therapy for patients with relapsed/refractory multiple myeloma,” said James Caruso, president and CEO of Cellectar, in a statement. “Patients with third-line or later relapsed/refractory multiple myeloma have a poor prognosis and low rates of survival as a result of limited effective treatment options. Based on data in the initial patient cohort from our ongoing CLOVER-1 trial where patients showed a 30% response rate after receiving a single 25.0 mCi/m²dose as a seventh line of therapy on average, we are optimistic that CLR 131 has the potential to provide a meaningful treatment option for these patients.”

CLR 131 is a small-molecule radiotherapeutic phospholipid drug conjugate that directs cytotoxic radiation to cancer cells and cancer stem cells. The drug conjugate consists of the CLR1404 cancer-targeted small molecule compound that is radiolabeled with the isotope iodine-131.

The CLOVER-1 trial is enrolling patients with relapsed or refractory B-cell malignancies, including multiple myeloma, indolent chronic lymphocytic leukemia, small lymphocytic lymphoma, lymphoplasmacytic lymphoma, marginal zone lymphoma, mantle cell lymphoma, and diffuse large B-cell lymphoma. Patients with multiple myeloma enrolled in the trial were required to have received at least 2 prior treatment regimens including at least 1 proteasome inhibitor and at least 1 immunomodulatory drug with or without maintenance therapy. The primary endpoint for the trial is clinical benefit rate with secondary endpoints of overall response rate (ORR), time to progression, and overall survival.

In early results from the multiple myeloma cohort of the CLOVER-1 trial,²the company announced that in the first 10 evaluable patients who received a single 30-minute infusion of CLR 131 at 25 mCi/m², an ORR of 30% was achieved. Additionally, 1 patient in the cohort had a very good partial response and 2 others had partial responses. All other patients in the cohort had at least stable disease.

Results from an ongoing, open-label phase I dose-escalation study of CLR 131 in patients with relapsed or refractory multiple myeloma demonstrated positive efficacy data for the agent.³

The trial is assessing the safety and tolerability of CLR 131 when administered as either a single dose or in split dose infusion(s) in heavily pretreated patients. Most patients had advanced stage II or III disease and had received an average of 5 prior treatment regimens, including anti-CD38, immunomodulatory drugs, and proteasome inhibitors. Fifteen patients were enrolled into 1 of 4 cohorts to receive doses between 12.5 mCi/m²and 31.25 mCi/m². Cohorts 5 and 6 were added at later dates to study CLR 131 at a fractionated dose of 31.25 mCi/m²and in 2 doses of 18.75 mCi/m², respectively.

In cohorts 1 through 4, patients demonstrated a median overall survival of 22 months. This was considered significant in comparison with historical data for patients with relapsed or refractory multiple myeloma treated in the third line.

References:

1. Cellectar receives FDA fast track designation for CLR 131 in relapsed or refractory multiple myeloma [press release]. Florham Park, NJ: Cellectar Biosciences Inc; May 13, 2019. https://bit.ly/2W4hjVJ. Accessed May 13, 2019.
2. Cellectar reports positive top-line response rate of 30% from R/R multiple myeloma cohort in ongoing phase 2 study of CLR 131 [press release]. Florham Park, NJ: Cellectar Biosciences Inc; February 25, 2019. https://bit.ly/2H5vwK3. Accessed May 13, 2019.
3. Cellectar provides update on phase 1 trial of CLR 131 in relapsed/refractory multiple myeloma [press release]. Florham Park, NJ: Cellectar Biosciences Inc; January 7, 2019. https://bit.ly/2WHzjSN. Accessed May 13, 2019.