Imugene Ltd (ASX:IMU, OTC:IUGNF) has fielded encouraging early results from its Phase 1 MAST (Metastatic Advanced Solid Tumours) trial.
The trial has been set up to evaluate the safety and efficacy of its novel cancer-killing virus CF33-hNIS (VAXINIA), administered alone or in combination with pembrolizumab, and dosed either intravenously (IV) or intratumourally (IT).
Well-tolerated and safe
As of January 12, the trial has treated 38 heavily pre-treated patients with the CF33-hNIS virus. The treatments have been well-tolerated and deemed safe.
Notably, one patient with biliary tract cancer achieved a Complete Response (CR) after being treated at a mid-dose level and has remained in remission for over 430 days.
Additionally, two Partial Responses (PRs) were observed in melanoma patients at a mid-dose level.
In the IT cohorts, 47% of injected lesions showed a reduction in tumour burden, with three lesions completely eradicated.
Among the IV cohorts, 53% of patients achieved stable disease as their best response.
Notably, seven patients with gastrointestinal cancers, treated with CF33-hNIS alone during dose escalation, showed a disease control rate (CR, PR, or SD) of 86%.
Early results of the study were presented this week at the American Society of Clinical Oncology - Gastrointestinal Cancer Symposium (ASCO-GI) in San Francisco, California.
The trial expansion plans include 10-20 patients with biliary tract cancers, which are often difficult to treat and typically show modest response to immunotherapy drugs.
Patients who had received prior checkpoint blockade therapy derived clinical benefits with and without pembrolizumab.
Complete response achieved
A striking case in the study involved a patient with biliary tract cancer who experienced pseudoprogression, initially showing a 49% increase in tumour burden after two cycles of therapy.
By the fourth cycle, the patient achieved a Complete Response with no known recurrence for more than 430 days.
Pseudoprogression is a phenomenon where the cancer initially appears to be growing due to virus-infected cancer cells and subsequent immune cell infiltration. It can mislead assessments of treatment effectiveness.
Understanding this phenomenon is crucial when assessing patient responses in immunotherapy because it can lead to premature discontinuation of treatment.
CEO and managing director Leslie Chong said: “This latest data reinforces the early positive responses we’ve seen in gastrointestinal cancers and in particular for cholangiocarcinoma (bile duct cancer).
"It provides an excellent platform to investigate the impact of VAXINIA at higher dose levels as we also expand the trial to additional patients with hard-to-treat biliary tract cancers.
"It is a proud moment for us to be able to present these results at ASCO-GI, and promote the potential of VAXINIA and CF33 more broadly.”