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Micrograph showing MM

ROME—Early results of a pilot study indicate that a 3-agent combination regimen can produce responses in patients with relapsed or refractory multiple myeloma (MM).

The treatment consists of carfilzomib, dexamethasone, and pelareorep (Reolysin), a proprietary isolate of human reovirus (Type 3 Dearing strain).

All 8 evaluable patients treated with this regimen experienced an objective response, although 1 patient later progressed.

The investigators said the regimen has been relatively well tolerated, but most patients experience flu-like symptoms over the first week of treatment. And cytopenias, especially thrombocytopenia, are common.

Douglas Sborov, MD, of The Ohio State University in Columbus, and his colleagues presented this research at the 15th International Myeloma Workshop (poster #379).

The investigators noted that this is the first time a pelareorep-based combination has been tested in relapsed MM patients. A previous single-agent study indicated that pelareorep was well tolerated, and preclinical research has shown that reovirus and carfilzomib synergize to kill MM cells.

To expand upon these results, Dr Sborov and colleagues began testing pelareorep with carfilzomib and dexamethasone in patients with relapsed/refractory MM. The ongoing study, known as NCI-9603, is sponsored by the National Cancer Institute.

Of the 8 patients enrolled thus far, 5 had intermediate- or high-risk disease at baseline, and 1 patient was dialysis-dependent. The median age was 63 (range, 43-70).

Patients had received a median of 2 prior lines of therapy (range, 1-6) and a median of 4 prior treatments (range, 2-8). All of the patients had received lenalidomide, 1 had received carfilzomib, and 4 were refractory to bortezomib.

For the current study, patients were assigned to receive dexamethasone, carfilzomib over 10 minutes, and pelareorep over 60 minutes on days 1, 2, 8, 9, 15, and 16. Treatment is set to repeat every 28 days in the absence of disease progression or unacceptable toxicity.

Patients who achieve a minimal response or better may reduce treatment to days 1, 8, and 15 after 4 courses and to days 1 and 15 after 12 courses.

Treatment results

The investigators said the treatment produced a significant (P=0.005) increase in caspase-3, a marker associated with apoptotic cell death.

The combination was also associated with an increased infiltration of CD8+ T cells and the significant (P=0.005) upregulation of PD-L1, suggesting the addition of a PD-1 or PD-L1 inhibitor might further optimize the regimen.

All 8 patients experienced an objective response to treatment, as measured by changes in blood monoclonal protein. Two patients had a very good partial response, 3 had a partial response, and 3 had a minor response.

Five of the patients remain on study. The dialysis-dependent patient discontinued treatment due to progression after 3 treatment cycles. And 2 patients discontinued treatment due to dose-limiting toxicities after 2 doses.

One of the patients with dose-limiting toxicities had grade 4 myocarditis, grade 3 left ventricular dysfunction, and grade 4 respiratory failure possibly attributable to pelareorep and carfilzomib. The other patient had lower gastrointestinal bleeding that was not attributed to treatment.

Adverse events in cycle 1 that were possibly, likely, or definitely attributed to treatment included hypertension (n=5), thrombocytopenia (n=4), anemia (n=4), dyspnea on exertion (n=4), fatigue (n=4), myalgia (n=3), fever (n=2), leukopenia (n=2), lymphopenia (n=2), nausea (n=2), and diarrhea (n=2).

For more details, visit the Oncolytics Biotech Inc. website to view the poster. Oncolytics is the company developing pelareorep. end hematology article

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