Replimune Group has commenced patient enrolment in a Phase II clinical trial being conducted to assess its Immulytic product candidate RP1.

The drug candidate will be investigated in combination with Libtayo (cemiplimab-rwlc) and developed by Regeneron and Sanofi to treat cutaneous squamous cell carcinoma (CSCC).

RP1 is based on a herpes simplex virus strain designed to enhance anti-tumour immune response, potency to kill tumours and immunogenicity of tumour cell death.

Libtayo is an anti-PD-1 drug approved by the US Food and Drug Administration (FDA) for use in metastatic CSCC or locally-advanced CSCC patients who cannot receive curative surgery or radiation.

The registration-directed, randomised, multi-centre, controlled Phase II trial will compare the combination of RP1 and Libtayo with Libtayo alone in around 240 patients.

Sites in the US and Australia are currently open for enrolment, with plans to add sites in other countries. The enrolment is estimated to be completed in 18-24 months.

The trial is being performed in alliance with Regeneron and will assess treatment response rate as the primary objective.

Next year, Replimune intends to conduct a Phase Ib trial of RP1 as monotherapy in about 30 liver and kidney transplant recipients with recurrent CSCC.

The protocol of the Phase Ib trial has been accepted by the FDA.

Replimune president and CEO Robert Coffin said: “We are pleased to announce the initiation of our first registration-directed clinical trial for which we believe the data generated to date for RP1 in CSCC is strongly supportive.

“Having reviewed the initial data in CSCC, we also intend to initiate a new clinical trial of single-agent RP1 in organ transplant recipients with CSCC, which we expect to begin enrolling early next year.”

RP1 has been evaluated alone, as well as in combination with Opdivo (nivolumab) in a Phase I/II trial.

The Phase I part of the trial involved 36 heavily pre-treated cancer patients, while the Phase II part enrolled 30 patients with melanoma and non-melanoma skin cancers, bladder cancer and MSI-H tumours. Five CSCC patients were also part of the trial.