Biothera Release: Imprime PGG-MAb Combination Therapy Achieves High Response Rate In Patients With Chronic Lymphocytic Leukemia

CHICAGO--(BUSINESS WIRE)--A combination of Biothera’s Imprime PGG and the monoclonal antibodies alemtuzumab and rituximab achieved responses in 13 of 14 (93%) patients with high-risk chronic lymphocytic leukemia, including nine (64%) complete responses. Results of this phase 1/2 study will be presented today at the American Society of Clinical Oncology (ASCO).

“A Phase (Ph) 1/2 Trial of Rituximab (RX), Imprime PGG (IP), and Alemtuzumab (AL) in the Early Treatment of Patients (Pts) with High Risk Chronic Lymphocytic Leukemia (CLL).”

Imprime PGG is an investigational cancer immunotherapy that directly modulates the key effector cells of the innate immune system, neutrophils, monocytes and macrophages, enabling them to recognize and kill antibody-targeted cancer cells. Recent research supports the potential of Imprime PGG to orchestrate a coordinated anti-tumor response involving both the innate and adaptive immune systems.

In previous studies, researchers observed a 37% complete response rate with alemtuzumab and rituximab combination treatment in patients with high-risk chronic lymphocytic leukemia. Results from the phase 1 portion of this study showed that the addition of Imprime PGG to this antibody regimen was well tolerated and associated with 73% complete response rate, meaning blood tests found no trace of cancer. (Blood 120: abstr 1792, 2013).

The primary endpoint of the second phase of the study was the percentage of patients with a complete response three months after completing five weeks of Imprime PGG plus alemtuzumab and rituximab treatment. Among the 14 patients enrolled in phase 2, all had chronic lymphocytic leukemia with high-risk features (including 17p13- [21%] and 11q22- [36%]).

Overall, 13 out of 14 (93%) patients had an objective response to the treatment combination, with 9 patients (64%) achieving a complete response. These responses were durable: 7 of 9 patients who obtained a complete response were progression-free at the time of the analysis and did not require additional treatment.

Among potential mechanisms of anti-tumor activity, researchers showed an increase in macrophage-mediated, antibody-dependent cellular phagocytosis (ADCP) of rituximab-treated lymphoma cells with Imprime PGG.

The most common adverse events on the combination treatment were anemia, rash and neutropenia. The addition of Imprime PGG to rituximab and alemtuzumab was safe and well tolerated.

The researchers concluded that the combination of Imprime PGG with rituximab and alemtuzumab may be a useful approach for patients with high risk chronic lymphocytic leukemia to extend the time until they need to undergo combination chemotherapy – an outcome that is particularly valuable for patients who would be unlikely to tolerate chemotherapy, such as the elderly or those with co-morbidities.

“These results provide exciting proof of concept for combining Imprime PGG with rituximab or alemtuzumab in patients with hematological malignancies” said Ada Braun, M.D., Ph.D., Chief Medical Officer at Biothera. “Biothera will continue to explore indications with high unmet clinical needs where Imprime PGG can make a difference.”

Biothera will present the new data in a poster session from 8:00 am to 11:30 am CST today in S Hall A (Poster board # 67). The poster title is “A Phase (Ph) 1/2 Trial of Rituximab (RX), Imprime PGG (IP), and Alemtuzumab (AL) in the Early Treatment of Patients (Pts) with High Risk Chronic Lymphocytic Leukemia (CLL).”

About Biothera

Biothera is a privately held biotechnology company developing Imprime PGG, a late clinical stage immunotherapeutic drug candidate that modulates key immune cells to recognize and kill cancer. Proof of concept has been established from randomized and single-arm Phase 2 studies in non-small cell lung cancer (NSCLC), colorectal cancer, and chronic lymphocytic leukemia. In the NSCLC study, which evaluated the addition of Imprime PGG to bevacizumab and carboplatin/paclitaxel versus bevacizumab and chemotherapy alone, objective response rate was 60.4% versus 43.5%, duration of response was 10.3 months versus 5.6 months and median overall survival was 16.1 months versus 11.6 months. Studies are ongoing in metastatic colorectal cancer and non-Hodgkin lymphoma.

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