The study, enrolled 59 patients with previously treated advanced or metastatic disease and a high likelihood of tumor 5T4 expression. The primary objective was to evaluate the safety, tolerability and determining the maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of naptumomab in combination with checkpoint inhibitor (CPI) durvalumab. Secondary objectives included antitumor activity and duration of response based on RECIST 1.1/iRECIST of the combination. Obinutuzumab pre-treatment was used to inhibit the formation of anti-drug-antibodies (ADAs). The results from the dose-escalation and MTD - expansion part of the study show that naptumomab at the RP2D of 10mcg/kg in combination with durvalumab is generally well tolerated with limited toxicity. Preliminary results show that pre-treatment with obinutuzumab reduces the formation of ADAs and preserves naptumomab plasma levels. Durable responses were seen, including complete responses in patients, where response to single agent CPI was not expected. In the next step cohort expansion in patients with esophageal cancer is planned.

"I am excited about naptumomab's potential to synergize with checkpoint inhibitors ("CPI"). Naptumomab`s ability to bring activated T cells to the tumor, remodel the tumor microenvironment, act as a neoantigen mimetic, induce epitope spreading and long-term memory response, along with an acceptable safety profile makes naptumomab a good fit with checkpoint inhibitor therapy, especially for patients whose profile typically do not respond to immunotherapy." Asher Nathan, CEO of NeoTX Therapeutics.

The abstract Safety and Preliminary Activity of Naptumomab Estafenatox (NAP) and Durvalumab in Patients with Advanced or Metastatic Solid Tumors - Interim Results from a Phase 1b Trial is available on the American Association for Cancer Research (AACR) Annual Meeting 2023 webpage https://www.abstractsonline.com/pp8/#!/10828/presentation/10341.

For more information on the trial, visit www.clinicaltrials.gov NCT03983954