TUSTIN, CA  02/13/13 — Peregrine Pharmaceuticals  announced results from its 70 patient open-label, randomized Phase II clinical trial of bavituximab used in combination with gemcitabine in patients with previously untreated, advanced Stage IV pancreatic cancer. The trial included the enrollment of patients with advanced metastatic disease including significant liver involvement and poor performance status associated with rapid disease progression. Results showed that the combination of bavituximab and gemcitabine resulted in more than a doubling of overall response rates (ORR) and an improvement in overall survival (OS) when compared with gemcitabine alone (control arm). In the trial, patients treated with a combination of bavituximab and gemcitabine had a 28% tumor response rate as compared to 13% in the control arm. Median OS, the primary endpoint of the trial, was 5.6 months for the bavituximab plus gemcitabine arm and 5.2 months for the control arm (hazard ratio = 0.75).

Bavituximab binds to phosphatidylserine which is exposed on the surface of certain atypical animal cells, including tumour cells and cells infected with any of six different families of virus. These viral families contain the viruses hepatitis C, influenza A and B, HIV 1 and 2, measles, respiratory syncytial virus and pichinde virus, which is a model for the deadly Lassa virus.^[2] Other cells are not affected since phosphatidylserine normally is only intracellular.^[3]

Bavituximab binds to various aminophospholipids and is dependent on interaction with plasma protein beta-2 glycoprotein I to mediate binding.

These target aminophospholipids, usually residing only on the inner leaflet of the plasma membrane of cells, become exposed in virally infected, damaged or malignant cells, and more generally in most cells undergoing the process of apoptosis.

The antibody’s binding to phospholipids alerts the body’s immune system to attack the tumor endothelial cells, thrombosing the tumor’s vascular network and/or attacking free floating virally infected and metastatic cells while potentially minimizing side effects in healthy tissues.

1. Statement on a nonproprietary name adopted by the USAN council
2. Nature Medicine 14, 1357 – 1362 (2008)
3. He, J.; Yin, Y.; Luster, T. A.; Watkins, L.; Thorpe, P. E. (2009). “Antiphosphatidylserine Antibody Combined with Irradiation Damages Tumor Blood Vessels and Induces Tumor Immunity in a Rat Model of Glioblastoma”. Clinical Cancer Research 15 (22): 6871–6880. doi:10.1158/1078-0432.CCR-09-1499. PMID 19887482. edit
4. New Progression-Free Survival Data From Peregrine’s Bavituximab in Phase II Refractory Breast Cancer
5. Phase II Advanced Breast Cancer Data to Be Presented at ASCO Highlight Promising Tumor Response and Progression-Free Survival Data With Peregrine’s Bavituximab
6. Pharma company completes humanization of 3G4 antibody
7. He, J.; Luster, T. A.; Thorpe, P. E. (2007). “Radiation-Enhanced Vascular Targeting of Human Lung Cancers in Mice with a Monoclonal Antibody That Binds Anionic Phospholipids”. Clinical Cancer Research 13 (17): 5211–5218. doi:10.1158/1078-0432.CCR-07-0793. PMID 17785577. edit
8. Ran; Downes, A.; Thorpe, P. E. (2002). “Increased exposure of anionic phospholipids on the surface of tumor blood vessels”. Cancer Research 62 (21): 6132–6140. PMID 12414638.

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