Imprime PGG and cetuximab increase overall response rate in metastatic colorectal cancer

A combination of Biothera's Imprime PGG® and cetuximab (Erbitux®) doubled the overall response rates for second- and third-line metastatic colorectal cancer patients participating in a Phase Ib/IIa clinical trial. The completed trial results were released yesterday at the 35^th European Society for Medical Oncology (ESMO) Congress.

“The results of this dual arm study demonstrate the proof of concept the Imprime PGG is a novel drug that engages and directs innate immune cells to kill cancer”

The sequential, dual-arm, open-label, dose-escalation study evaluated the safety and efficacy of Imprime PGG plus cetuximab and irinotecan (Arm #1) or Imprime PGG plus cetuximab alone (Arm #2). The 32-patient trial was conducted in Asia. In both arms of the trial, patients were dosed with 2 mg/kg, 4 mg/kg or 6 mg/kg of Imprime PGG in combination with standard doses of cetuximab and irinotecn. Imprime PGG was safe and well tolerated.

All tumor responses and duration of responses were based on Response Evaluation Criteria in Solid Tumors (RECIST), Version 1.0.

Study Arm 1 Results
This portion of the study compared the combination of Imprime PGG, cetuximab and irinotecan to the standard of care of cetuximab and irinotecan alone for these late-stage patients. The trial results from this Arm demonstrated a doubling of the historical overall response rate and a two-month extension in the time to progression of these patients, compared with cetuximab and chemotherapy.

* EPIC Study (Sobrero et al., JCO, 2008)
** Biothera Study

Study Arm 2 Results
This portion of the trial compared the combination of Imprime PGG and cetuximab with cetuximab monotherapy. Chemotherapy was not administrated to avoid the unintentional destruction of immune cells that are integral to Imprime PGG's mechanism of action. The trial results from this Arm demonstrated a doubling of the historical overall response rate and the time to progression of these patients, compared with cetuximab monotherapy.

* Erbitux (cetuximab) alone data from the BOND study, Cunningham et al., NEJM 2004.

Subpopulation Results
The study also retrospectively looked at subpopulations of the colorectal cancer patients based on those whose tumors expressed wild type versus mutated KRAS genes. In the wild type KRAS patient population responses were even more pronounced as shown below.

* Erbitux (cetuximab) alone KRAS wild type data represent the mean of response data reported from 4 published studies (Khambata JCO 2007, DeRook Ann Oncol 2008, Lurje Clin Cancer Res 2008, Karapetis NEJM 2008; Total subjects from all Studies = 262.)

"The results of this dual arm study demonstrate the proof of concept the Imprime PGG is a novel drug that engages and directs innate immune cells to kill cancer," said Dan Conners, president of Biothera's Pharmaceutical Group. "Imprime PGG's ability to engage the innate immune system opens the door to numerous new therapeutic combinations with monoclonal antibodies targeting the vast majority of cancers."