The Efficacy and Safety of PRTX007-003 Combined With Pembrolizumab in Resectable Stage III Melanoma (INFLECTION-003)

A Phase 2 Study to Investigate the Activity of Neoadjuvant PRTX007 Combined With Pembrolizumab in Participants With Stage III Melanoma (INFLECTION-003)

This Phase 2, multi-center, single-arm study evaluates the safety, tolerability, and activity of neoadjuvant PRTX007 in combination with pembrolizumab in participants with resectable Stage III melanoma. Neoadjuvant immunotherapy has demonstrated improved clinical outcomes compared with adjuvant-only approaches, but there remains a need to enhance pathologic response rates without significant added toxicity.

Participants will receive oral PRTX007, a Toll-like receptor 7 (TLR7) agonist prodrug, administered in combination with intravenous pembrolizumab prior to surgical resection. The primary objective is to determine the major pathologic response (MPR) rate following neoadjuvant therapy. Secondary objectives include evaluation of safety, pathologic complete response, event-free survival, overall survival, pharmacokinetics, and immune-related biomarkers.

This study aims to determine whether the addition of PRTX007 to pembrolizumab improves antitumor immune responses and clinical outcomes in patients with Stage III melanoma.

Study Overview

• Status: Not yet recruiting
• Conditions: Melanoma Stage III
• Intervention / Treatment: Drug: PRTX007; Drug: Pembrolizumab

Detailed Description

This study investigates whether combining the TLR7 agonist PRTX007 with pembrolizumab enhances immune-mediated tumor response in the neoadjuvant setting for Stage III melanoma, with the goal of improving pathologic response rates and clinical outcomes while maintaining an acceptable safety profile.

Design This is a Phase 2, multi-center, open-label, single-arm study conducted in Australia. The study will enroll approximately 48 participants with resectable Stage III melanoma.

The study consists of two parts:

• Part A: 24 participants will be enrolled, including an initial dose-escalation safety run-in using a 3+3 design to evaluate tolerability and dose-limiting toxicities.
• Part B: An additional 24 participants will be enrolled if sufficient activity is observed in Part A.

Treatment Plan

Participants will receive neoadjuvant therapy consisting of:

• PRTX007: Oral administration for 3 days on and 4 days off per week for 9 cycles (7-day cycles)
• Pembrolizumab: 200 mg intravenous infusion every 3 weeks for 3 cycles Following completion of neoadjuvant therapy, participants will undergo definitive surgical resection.

Post-surgical treatment will be response-adapted:

• Participants achieving MPR may receive observation or pembrolizumab alone
• Participants without MPR will receive adjuvant PRTX007 in combination with pembrolizumab

• Study Type: Interventional
• Enrollment (Estimated): 48
• Phase: Phase 2

Contacts and Locations

• Study Contact: Name: Shinam Garg; Phone Number: +61-2-9171-3260; Email: Shinam.garg@novotech-cro.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Adults aged 18 years or older
• Histologically confirmed, resectable Stage III cutaneous melanoma.
• Candidate for curative-intent surgical resection
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
• Adequate organ function
• Able to provide written informed consent

Exclusion Criteria:

• Prior systemic therapy for melanoma, including immunotherapy
• Uveal melanoma or mucosal melanoma.
• Active autoimmune disease requiring systemic treatment
• Primary immunodeficiency or use of systemic immunosuppressive therapy
• Women who are pregnant or breastfeeding
• Recent treatment with another investigational therapy
• Any condition that, in the opinion of the investigator, would interfere with study participation or safety

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Neoadjuvant PRTX007 + Pembrolizumab (Response-Adapted Adjuvant Therapy); Participants with resectable Stage III melanoma will receive neoadjuvant treatment with PRTX007 in combination with pembrolizumab prior to definitive surgical resection. Following surgery, participants will receive response-adapted adjuvant therapy based on pathologic response. Participants achieving a major pathologic response (MPR) may receive observation or pembrolizumab alone, while participants without MPR will receive adjuvant PRTX007 in combination with pembrolizumab.

Drug: PRTX007; PRTX007 is an orally administered prodrug of PRX034, a Toll-like receptor 7 (TLR7) agonist designed to activate innate and adaptive immune responses. NEOADJUVANT REGIMEN; 600 mg orally once daily (safety run-in participants) or; 750 mg orally once daily (subsequent participants); Administered 3 days on, 4 days off (7-day cycle); Total of 9 cycles (9 weeks) ADJUVANT REGIMEN (IF NO MPR); 750 mg orally once daily; Administered 3 days on, 4 days off; Total of 12 cycles (12 weeks); Drug: Pembrolizumab; Pembrolizumab is a programmed cell death protein-1 (PD-1) blocking antibody administered by intravenous infusion NEOADJUVANT REGIMEN; 200 mg IV every 3 weeks (Q3W); Total of 3 cycles (9 weeks) ADJUVANT REGIMEN; 400 mg IV every 6 weeks (Q6W) for 7 cycles OR; 200 mg IV every 3 weeks (Q3W) for 14 cycles; Total duration: approximately 42 weeks

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Major Pathologic Response (MPR) Rate	Major pathologic response (MPR) is defined as ≤10% residual viable tumor cells in the resected tumor specimen following completion of neoadjuvant therapy, as assessed by central pathology review.	At time of surgical resection (approximately 9 weeks after initiation of treatment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incidence of Adverse Events (AEs), Serious Adverse Events (SAEs), Immune-Related AEs (irAEs), and Dose-Limiting Toxicities (DLTs)	Number and severity of adverse events, serious adverse events, immune-related adverse events, and dose-limiting toxicities, graded according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version 6.0.	From first dose of study treatment through end of study (approximately up to 52 weeks)
Number of participants with abnormal physical examination findings, abnormal vital signs, abnormal Eastern Cooperative Oncology Group (ECOG) performance status, and abnormal clinical laboratory parameters		Baseline through end of study (approximately up to 52 weeks)
Pathologic Complete Response (pCR) Rate	Pathologic complete response (pCR) is defined as the absence of residual viable tumor cells (0%) in the resected tumor specimen following neoadjuvant therapy, as assessed by central pathology review.	At time of surgical resection (approximately 9 weeks after initiation of treatment)
Event-Free Survival (EFS)	Event-free survival (EFS) is defined as the time from first dose of study treatment to any of the following events: disease progression or toxicity preventing surgery during neoadjuvant treatment; recurrence of disease after surgery; failure to achieve complete resection (R0 or R1); or death from any cause.	From first dose up to 1 year
Overall Survival (OS)	Overall survival is defined as the time from first dose of study treatment to death from any cause.	From first dose through end of study (approximately up to 52 weeks or longer if followed)
Pharmacokinetics of PRTX007	Plasma concentrations of PRTX007 and its active metabolite will be measured to characterize pharmacokinetic parameters using validated analytical methods.	During treatment period (multiple time points from baseline through approximately 9 weeks and selected later time points)
Changes in cytokine, chemokine and soluble PD-1/PD-L1 biomarkers		Baseline through treatment period (up to approximately 9 weeks and selected later time points)
Changes in mRNA expression		Baseline through treatment period (up to approximately 9 weeks and selected later time points)
Changes in immune cell activation and proliferation markers		Baseline through treatment period (up to approximately 9 weeks and selected later time points)

Collaborators and Investigators

• Sponsor: Primmune Therapeutics, Inc.

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2026
• Primary Completion (Estimated): December 1, 2027
• Study Completion (Estimated): June 1, 2029

Study Registration Dates

• First Submitted: April 20, 2026
• First Submitted That Met QC Criteria: April 27, 2026
• First Posted (Actual): May 4, 2026

Study Record Updates

• Last Update Posted (Actual): May 4, 2026
• Last Update Submitted That Met QC Criteria: April 27, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Neoplasms by Histologic Type; Skin Diseases; Neuroectodermal Tumors; Neoplasms, Germ Cell and Embryonal; Neoplasms, Nerve Tissue; Neuroendocrine Tumors; Nevi and Melanomas; Skin Neoplasms; Skin and Connective Tissue Diseases; Melanoma; pembrolizumab
• Other Study ID Numbers: PRTX007-003

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data will not be shared because the study involves an investigational product and the sponsor has not established a data sharing plan at this time.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No