Onchilles Pharma Advances in Situ Cancer Vaccine Strategy with N17350

Onchilles Pharma has reported preliminary clinical findings from OP-NEU-101, its Phase 1/2 trial of intratumoral N17350 in patients with advanced solid tumours. The findings, which will be presented at the 41st Annual Meeting of the Society for Immunotherapy of Cancer (SITC) on November 7, 2026, provide an early clinical assessment of an approach designed to use a patient’s own tumour as the source of antigens for a systemic immune response.

N17350 is an investigational engineered therapeutic elastase derived from research into cancer-selective enzymes. Administered directly into a tumour, it is designed to destroy cancer cells and release tumour antigens that may stimulate the immune system to recognise and attack cancer elsewhere in the body. The approach aims to generate a personalised immune response without requiring tumour sequencing, antigen selection or individualised vaccine manufacturing.

Five Non-Injected Lesions Become Undetectable

The most notable early evidence of clinical activity came from a patient with Merkel cell carcinoma, a rare and aggressive skin cancer that had progressed despite previous avelumab-based treatment and radiotherapy.

Investigators injected N17350 into one of six lesions included in the assessment. At Week 8, all five non-injected lesions were no longer detectable on the investigator’s RECIST 1.1 assessment. These comprised one lesion selected for precise measurement and four additional lesions monitored for their presence or absence.

FDG-PET imaging also showed a 56% to 60% reduction in maximum standardised uptake value (SUVmax) across the evaluated lesion groups, indicating reduced metabolic activity. An independent radiology assessment of a separate lesion also identified reduced FDG uptake.

The findings suggest potential antitumour activity beyond the directly treated lesion. However, the observation comes from a single patient and does not establish a confirmed complete response or demonstrate efficacy across the broader study population.

Initial Safety and Pharmacokinetic Findings

In the first dose cohort, three heavily pretreated patients received N17350 at a concentration of 1 mg/mL. All three completed the dose-limiting toxicity assessment period without experiencing dose-limiting toxicities, supporting progression to the next dose level.

Preliminary pharmacokinetic analysis detected no active N17350 enzyme in plasma at any sampled time point. Investigators also reported no treatment-emergent anti-drug antibodies.

Initial immune profiling in the patient with Merkel cell carcinoma showed a shift towards an effector-dominant and less immunosuppressive immune profile. Together, these observations are consistent with the possibility that local tumour treatment stimulated an immune response contributing to activity in non-injected lesions.

Nevertheless, the available findings do not establish the precise mechanism responsible for the observed distant lesion responses.

N17350: An In Situ Cancer Vaccination Approach

N17350 builds on research into neutrophil elastase and cancer-selective cell destruction. The investigational therapy is designed to exploit a vulnerability associated with altered histone H1 biology in cancer cells, while largely preserving non-cancer and immune cells.

Its proposed mechanism involves two complementary effects. First, direct injection into a tumour induces cancer cell destruction. Second, the resulting release of tumour antigens may help activate an adaptive immune response capable of recognising cancer cells at other sites.

This approach could offer a different route to personalised cancer immunotherapy. Rather than developing a separate vaccine for each patient, N17350 is designed to use antigens generated from the patient’s own tumour following treatment.

The clinical findings provide an initial human observation consistent with this concept, although its reproducibility and therapeutic potential remain to be established.

Clinical Development and Next Steps

OP-NEU-101 (NCT07339176) is a first-in-human, multicentre, open-label Phase 1/2 study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity and preliminary antitumour activity of intratumoral N17350.

The development programme includes dose-finding in patients with injectable superficial lesions, followed by evaluation in visceral lesions and potential tumour-specific expansion cohorts. Planned expansion indications include melanoma, cutaneous squamous cell carcinoma, head and neck squamous cell carcinoma, non-small cell lung cancer and triple-negative breast cancer.

The trial evaluates N17350 through intratumoral administration, with treatment schedules involving injections every two weeks for eight or twelve weeks.

The initial findings offer an early clinical signal for Onchilles Pharma’s proposed strategy of combining direct tumour destruction with potential systemic immune activation. The five-lesion observation is particularly notable because it suggests that treating one accessible tumour could potentially influence disease at other sites.

However, the evidence remains preliminary. Larger cohorts, additional tumour types and longer follow-up will be needed to determine whether the observed activity can be reproduced, whether responses are durable and whether N17350 can establish a clinically meaningful role in advanced solid tumours.

Reference

Onchilles Pharma Reports First Clinical Data at SITC 2026 That N17350 Could Turn One Tumor into a Personalized Cancer Vaccine, Onchilles Pharma, 06 November 2026

Intratumoral N17350 in Advanced Solid Tumors (OP-NEU-101), ClinicalTrials.gov ID NCT07339176