Novel Preclinical Studies with MabVax Therapeutics' HuMab-5B1 Antibody and HuMab-GD2 Antibodies Presented at the 2017 World Molecular Imaging Congress

SAN DIEGO, Oct. 3, 2017 /PRNewswire/ --MabVax Therapeutics Holdings, Inc. (Nasdaq: MBVX), a clinical-stage biotechnology company with a fully human antibody discovery platform focused on the rapid translation into clinical development of products to address unmet medical needs in the treatment of cancer, announced today that data from its HuMab-5B1 and HuMab-GD2 antibody programs were presented at the 2017 World Molecular Imaging Congress (WMIC) held September 13-16, 2017, in Philadelphia, PA. Results from these studies provide additional evidence of the targeting specificity, affinity, and potential utility of the Company's antibodies derived from patients' immune response to administered cancer antigen vaccines. Results from the HuMab-5B1 imaging work indicate the Company's HuMab-5B1 antibody had improved tumor accumulation compared to a comparator antibody, which is commercially available.

Novel preclinical applications for HuMab-5B1 investigated at Dr. Jason Lewis's Lab at Memorial Sloan Kettering Cancer Center were highlighted at the meeting.

• Research Fellow Sophie Poty, Ph.D., presented her work using the HuMab-5B1 antibody as a targeting agent in conjunction with an alpha-emitter radioimmunotherapy in preclinical models for pancreatic ductal adenocarcinoma. Biodistribution of standard pre-conjugated 5B1-225Ac-radioimmunoconjugates was compared with an alternative pre-targeting approach, whereby the radioimmunoconjugates are formed in vivo with 225Ac-DOTA-tertrazine derivatives. Equal tumor accumulation was seen in both, and decreased accumulation in liver and other organs after pre-targeting was observed. If developed further clinically, the pre-targeting approach could reduce potential toxicities experienced by patients with these critically important advanced therapies. 
• Research Scholar Nicholas Sobal, Ph.D., presented the first conjugation of HuMab-5B1 to gold nanoparticles. 5B1-gold-immunoconjugates showed significant, antigen-specific tumor accumulation in PDAC xenograft models and a favorable biodistribution profile. This work has implications for tumor delineation on PET/CT for more accurate treatment staging and potential for image-guided external beam radiation therapy.
• Outi Keinänen, a visiting graduate student from the University of Helsinki, investigated PET imaging and the biodistribution of HuMab-5B1 and Cetuximab in a pre-targeting approach with two structurally distinct fluorine-18 labelled tetrazine radiotracers. In preclinical models, increasing tumor accumulation of both radiotracers was observed with HuMab-5B1 over a 4-hour time period, with a peak tumor-to-blood ratio of ~ 4x at the last measured time point. In contrast, when Cetuximab was used for targeting, both radiotracers decreased over time on tumor and the maximal tumor-to-blood ratio was less than 1x. The results of the studies indicate that the use of the Company's HuMab-5B1 may represent an improved approach to pre-targeting.

In an ongoing collaboration with Dr. Scott Snyder at St. Jude Children's Hospital, MabVax is investigating the targeting specificity of two HuMab-GD2 ganglioside antibodies. These antibodies are part of the preclinical library of potential useful antibodies already discovered at MabVax. Dr. Wolfgang Scholz, VP, Antibody Discovery, presented the PET imaging data of ⁶⁴CU-NOTA-conjugated antibody 1B7 and antibody 31F9. In vitro profiling shows that both antibodies are readily internalized and both antibodies accumulate in GD2 positive patient-derived osteosarcoma xenografts within 48 hours. These data support further evaluation for the development of a PET imaging probe for sarcoma.

About the HuMab-5B1 Antibody

The Company's HuMab-5B1 antibody is fully human and was discovered from the immune response of cancer patients vaccinated with an antigen-specific vaccine during a Phase 1 trial at Memorial Sloan Kettering Cancer Center (MSK). The HuMab-5B1 antibody has excellent tumor targeting capabilities, as well as being internalized by pancreatic cancer cells. These important attributes have allowed us to use the HuMab-5B1 antibody as a tumor-targeting platform upon which we have created multiple products. The antibody itself is in a Phase 1 clinical trial as a therapeutic agent.

About MabVax

MabVax Therapeutics Holdings, Inc. is a clinical-stage biotechnology company with a fully human antibody discovery platform focused on the rapid translation into clinical development of products to address unmet medical needs in the treatment of cancer. Our antibody MVT-5873, is a fully human IgG1 monoclonal antibody (mAb) that targets sialyl Lewis A (sLea), an epitope on CA19-9, and is currently in Phase 1 clinical trials as a therapeutic agent for patients with pancreatic cancer and other CA19-9 positive tumors. CA19-9 is expressed in over 90% of pancreatic cancers and in other diseases including small cell lung and GI cancers. CA19-9 plays an important role in tumor adhesion and metastasis, and is a marker of an aggressive cancer phenotype. CA19-9 serum levels are considered a valuable adjunct in the diagnosis, prognosis and treatment monitoring of pancreatic cancer. With our collaborators including Memorial Sloan Kettering Cancer Center, Sarah Cannon Research Institute, Honor Health and Imaging Endpoints, we have treated 50 patients with either our therapeutic antibody designated as MVT-5873 or our PET imaging diagnostic product designated as MVT-2163 in Phase 1 clinical studies, and demonstrated early safety and specificity for the target. Patient dosing has commenced for our lead development program in Phase 1 clinical study of the Company's radioimmunotherapy product MVT-1075. For additional information, please visit the Company's website, www.mabvax.com.

Forward Looking Statements

This press release contains "forward-looking statements" regarding matters that are not historical facts, including statements relating to presentations at the WMIC. We have no assurance that all the product development pipeline will be fully developed by the Company. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Words such as "anticipates," "plans," "expects," "intends," "will," "potential," "hope" and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon current expectations of the Company and involve assumptions that may never materialize or may prove to be incorrect. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements because of various risks and uncertainties. Detailed information regarding factors that may cause actual results to differ materially from the results expressed or implied by statements in this press release relating to the Company may be found in the Company's periodic filings with the Securities and Exchange Commission, including the factors described in the section entitled "Risk Factors" in its annual report on Form 10-K for the fiscal year ended December 31, 2016, as amended and supplemented from time to time and the Company's Quarter Reports on Form 10-Q and other filings submitted by the Company to the SEC, copies of which may be obtained from the SEC's website at www.sec.gov. The parties do not undertake any obligation to update forward-looking statements contained in this press release.

Investor Contact

Jenene Thomas
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Phone: +1 (908) 938-1475
Email: [email protected]

SOURCE MabVax Therapeutics Holdings, Inc.

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