Oncothyreon
May 16, 2013

Oncothyreon Announces Data for L-BLP25 and PX-866 to be Presented at American Society of Clinical Oncology Meeting

SEATTLE, May 16, 2013 /PRNewswire/ - Oncothyreon Inc. (NASDAQ: ONTY) today announced that the following presentations of data for L-BLP25 (formerly known as Stimuvax) and PX-866 will take place at the American Society of Clinical Oncology (ASCO) 2013 Annual Meeting in Chicago:

Abstract #7500
START - A Phase III study of L-BLP25 cancer immunotherapy for unresectable stage III non-small cell lung cancer.
Charles A. Butts, MD, FRCPC
Oral Abstract Session - Lung Cancer
Tuesday, June 4
9:45 AM - 10:00 AM

Abstract #2053
Phase II study of PX-866 in recurrent glioblastoma.
Marshall W. Pitz, MD, FRCPC
General Poster Session - CNS tumors
Saturday, June 1
8:00 AM - 11:45 AM

Abstract #5042
NCIC CTG, IND-205: A phase II study of PX-866 in patients with recurrent or metastatic castration resistant prostate cancer (CRPC).
Sebastien J. Hotte, MD, MSc
General Poster Session - Genitourinary Cancer
Monday June 3
8:00 AM - 11:45 AM

L-BLP25 - In connection with the upcoming presentation, Oncothyreon today announced detailed results from the randomized Phase III START trial of the investigational MUC1 antigen-specific cancer immunotherapy L-BLP25 (formerly referred to as Stimuvax) in patients with unresectable, locally advanced Stage III non-small cell lung cancer (NSCLC). The trial was conducted by Merck Serono, a division of Merck KGaA, Darmstadt, Germany, under a license agreement with Oncothyreon. The primary endpoint of improving overall survival (OS) was not met. In a predefined subgroup of patients receiving initial concurrent chemoradiotherapy (CRT), a combination of chemotherapy and radiotherapy given at the same time, a median overall survival of 30.8 months versus 20.6 months was observed based on a post hoc analysis in patients treated with L-BLP25 versus placebo respectively (HR 0.78, 95% CI 0.64-0.95, p=0.016, n=806).

The START trial is assessing the safety, efficacy and tolerability of L-BLP25 in patients with unresectable, locally advanced Stage III NSCLC who have not progressed after initial CRT, which is the current standard of care. Before receiving treatment with either L-BLP25 or placebo in the START trial, two-thirds of patients had received concurrent CRT and one-third had received sequential CRT (radiotherapy started after completion of chemotherapy). The trial did not meet its primary objective of demonstrating a significantly improved OS with L-BLP25 compared to placebo in the primary analysis study population (n=1,239). Median OS was 25.6 months for patients in the L-BLP25 group compared with 22.3 months for those in the placebo group (adjusted HR 0.88, 95% CI 0.75-1.03, p=0.123). In a post hoc analysis of the predefined subgroup of patients receiving initial concurrent CRT (n=806), patients receiving L-BLP25 had a median OS of 30.8 months compared to patients receiving placebo, who had a median OS of 20.6 months [HR 0.78; 95% CI 0.64-0.95; p=0.016]). In patients receiving sequential CRT followed by L-BLP25 or placebo a median OS of 19.4 months was observed for the L-BLP25 group compared with 24.6 months for the placebo group (n=433; HR 1.12; 95% CI 0.87-1.44; p=0.38). Predefined subgroup analyses included, among others, disease stage (IIIA or IIIB), response to initial CRT (stable disease versus objective response), type of initial CRT (concurrent versus sequential) and geographic region.

Injection site reactions, a pre-defined group of adverse events, occurred in 17.3% of patients in the L-BLP25 group and in 11.9% of patients in the placebo group. Flu-like symptoms, another pre-defined group of adverse events, observed within 2 days after subcutaneous injection of study medication occurred in 10.9% of patients in the L-BLP25 group and in 9.9% of patients in the placebo group. Potentially immune-related diseases or events occurred at similar frequencies in both treatment groups. The most common adverse events ( > 10%) in subjects allocated to L-BLP25 were cough, dyspnea, fatigue, back pain, nausea, chest pain, nasopharyngitis, headache, decreased appetite and arthralgia, and in those allocated to placebo were cough, dyspnea, fatigue, back pain and headache. The most common grade 3 or 4 adverse event in both treatment groups was dyspnea (L-BLP25 group 4.8%, placebo group 4.4%).

"While the results from the primary analysis population were certainly not what we hoped for, I am encouraged by the results seen in the subgroup of patients receiving concurrent CRT followed by L-BLP25, particularly as concurrent CRT is the standard of care recommended for patients with unresectable Stage III NSCLC in both the National Compendium Cancer Network and European Society of Medical Oncology guidelines," said Dr. Charles Butts, Cross Cancer Institute, University of Alberta, Edmonton, Canada, clinical investigator and member of the START trial's steering committee. "This is the first time that an antigen-specific cancer immunotherapy has shown this effect in a substantial subgroup of NSCLC patients who are usually only observed following chemoradiotherapy."

PX-866 - Oncothyreon today also announced data from two single-arm Phase II trials of PX-866 in patients with glioblastoma (GBM) and castration resistant prostate cancer (CRPC), respectively.

In the GBM trial 33 patients with a first recurrence after chemoradiation and adjuvant temozolomide were given PX-866 8 mg daily. MRI and clinical exam were done every cycle (8 weeks). All patients were evaluable for response; 25 had a best response of progression, 1 had a partial response (overall response rate 3%) and seven (21%) had stable disease (median 7.3 months; range 3.1-13.6). Six month progression free survival was 17%.  PX-866 was relatively well tolerated.  Adverse effects included liver function test abnormalities, fatigue, diarrhea, nausea, vomiting and lymphopenia.

In the CRPC trial 43 patients not previously treated with docetaxel received PX-866, 8mg daily on a 6-week cycle. The primary endpoint was lack of progression at 12 weeks (PCWG2 criteria). Secondary endpoints included PSA and objective response rates and change in circulating tumor cells (CTC) during treatment. Eleven patients were progression free at 12 weeks. Sixteen of the 24 patients with measurable disease were evaluable for response; there were no objective responses but 10 patients had stable disease (2.6-13.9 months). One patient had a confirmed PSA response. CTC favorable conversion (from 5 at baseline to < 5) was observed in 6 of 24 evaluable patients (25%).  PX-866 was well-tolerated.  Adverse events included diarrhea, nausea, fatigue, vomiting, anorexia, hypomagnesemia  and liver function test abnormalities.  An extension of this trial in patients whose PSA is rising while being treated with abiraterone is ongoing.

About Oncothyreon

Oncothyreon is a biotechnology company specializing in the development of innovative therapeutic products for the treatment of cancer. Oncothyreon's goal is to develop and commercialize novel synthetic vaccines and targeted small molecules that have the potential to improve the lives and outcomes of cancer patients. For more information, visit www.oncothyreon.com.

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