MabVax Therapeutics Holdings, Inc. provided an important update on its HuMab-5B1 clinical program as well as presented preclinical data for its HuMab-Tn research program describing a new series of fully-human antibodies targeting ovarian and breast cancer at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics held October 26 - 30, 2017 in Philadelphia, Pennsylvania. Three posters were presented by Paul W. Maffuid, Ph.D., Executive Vice President of Research and Development, outlining important progress in the Company's lead fully human antibody programs, HuMab-5B1 currently in Phase 1 clinical development for the treatment of pancreatic cancer and other CA19-9 positive malignancies, and HuMab-Tn currently in preclinical development with potential clinical utility in breast and ovarian cancers. MVT-5873 in combination with nab-paclitaxel and gemcitabine as first line therapy - The company reported that newly diagnosed pancreatic cancer patients participating in the Phase 1 clinical trial of MVT-5873, when given in combination with first line nab-paclitaxel and gemcitabine, demonstrated reductions in tumor size after the first two months of therapy. The data reported from this dose escalation safety study included safety data from 7 patients at 1mg/kg and 0.125mg/kg. After the first cohort was treated at 1mg/kg, the MVT-5873 dose was reduced to 0.125 mg/kg in combination with nab-paclitaxel and gemcitabine as the lower dose appears to be generally well tolerated. Two of 3 patients at this lower dose had a partial response (PR) with the remaining patient recording stable disease (SD). One patient continues therapy after six-months. The company is currently enrolling an additional cohort of patients at the 0.125mg/kg cohort and expects to report on additional data near the end of this year. Utility of HuMab-5B1 (MVT-5873) in cancers beyond pancreatic cancer. At the AACR-NCI-EORTC meeting, the company presented a series of studies examining expression of CA19-9 on tumor microarrays (TMA) and patient derived tumor xenografts (PDX). The results support the expansion of clinical studies of MVT-5873 for the treatment of other CA19-9 positive malignancies, including colorectal, small cell lung and non-small lung cell cancers. Human colorectal (CRC) TMA samples displayed moderate to high levels of positive staining with MVT-5873 in >75% of tumor samples evaluated. MVT-5873 staining of PDX samples was positive in 21% of non-small cell lung cancer (NSCLC), 50% of small cell lung cancer (SCLC), and 69% of CRC cores evaluated. The study included PDX samples from patients with KRAS, BRAF, PIK3CA, or MMR pathway mutations and PDX samples rendered chemoresistant. These results support that expression of CA19-9 in these tumor types is unaffected by mutational status or treatment with chemotherapy. Based on these encouraging data, the company plans to enroll and treat patients in its ongoing clinical trials with tumor types beyond pancreatic cancer. The company has previously reported Phase 1a results for MVT-5873 as a single agent in pancreatic cancer patients.