Molecular Templates, Inc. Provides Update on MT-5111 Phase 1 Study

Phase 1 Study Dose Escalation Ongoing in All HER2 Positive Tumor Types
HER2 Positive Breast Cancer Expansion Cohort Planned to be Initiated in 1H21
Expansion Cohorts in Additional Tumors Types to Begin When MTD or Recommended Phase 2 Dose is Reached

AUSTIN, Texas, Dec. 21, 2020 (GLOBE NEWSWIRE) -- Molecular Templates, Inc. (Nasdaq: MTEM, “Molecular Templates,” “MTEM” or “the Company”), a clinical-stage biopharmaceutical company focused on the discovery and development of proprietary targeted biologic therapeutics, engineered toxin bodies (ETBs), today provided an update on the Phase 1 study for MT5111, MTEM’s HER2 targeted ETB.

To date, 16 study subjects have been treated in the dose escalation portion of this study. Five cohorts (0.5, 1.0, 2.0, 3.0, and 4.5 μg/kg/week) have been successfully completed and the sixth cohort (6.75 μg/kg) has been initiated. Pharmacokinetic (PK) data confirm the predicted human PK based on non-human primate studies. PK modeling has suggested that doses equal to or greater than 5.0 μg/kg are likely needed for efficacy.

Study subjects dosed to date had tumor types including metastatic breast cancer (n=6; two at 0.5 μg/kg, one at 1 μg/kg, one at 2 μg/kg, and two at 3 μg/kg), metastatic biliary tract carcinoma (n=6; two at 0.5 μg/kg, one at 1 μg/kg, two at 2 μg/kg, and one at 4.5 μg/kg), metastatic pancreatic cancer (n=2, both at 4.5 μg/kg), and one each of metastatic colon adenocarcinoma (3 μg/kg) and metastatic gastroesophageal junction adenocarcinoma (1 μg/kg). These study subjects had a median of four prior lines of therapy and a median of two prior HER2-targeting regimens; subjects with breast cancer received a median of six prior lines of therapy, four of which contained HER2-targeting agents.

MT5111 appears to be well tolerated with no dose limiting toxicities (DLTs) observed in any cohort. In particular, no signs of cardiotoxicity have been observed to date, while monitoring the subjects’ EKGs, troponin values and pro-BNP with each treatment, and serial echocardiograms with every other cycle. The most commonly reported adverse events (AEs) that may be causally related among the four dosing cohorts and for which source-verified data were available were: fatigue (n=3), AST increased (n=2) at 0.5 μg/kg and 1 μg/kg, and chills (n=2). These most commonly reported AEs were all of grade 1 or 2 severity. No cases of capillary leak syndrome (any grade) were observed.