Compass Therapeutics has announced the dosing of the first patient in a Phase Ib study of CTX-471 along with Merck’s (known as MSD outside the US and Canada) anti-PD-1 therapy KEYTRUDA (pembrolizumab) for advanced solid tumours.

Compass, which is also the study sponsor, supplied CTX-471, and KEYTRUDA will be provided by Merck as part of a clinical partnership and supply agreement signed by the companies.

The Phase Ib trial will enrol metastatic or locally advanced non-small cell lung cancer patients.

It will also include patients with melanoma, mesothelioma, small cell lung cancer, and head and neck cancer that have progressed following treatment with a checkpoint inhibitor.

Study participants will receive the CTX-471 and KEYTRUDA combination with the aim of restoring response.

Compass Therapeutics CEO and scientific founder Thomas Schuetz said: “We are very pleased to be making progress on our CTX-471 clinical programme with dosing of the first patient in the combination arm with KEYTRUDA.

“We are excited about the potential to build upon the responses observed with CTX-471 monotherapy across multiple tumour types and address significant unmet need in the field of cancer immunotherapy.”

The next generation, CD137 agonist, fully human, IgG4 antibody CTX-471 has an optimised affinity for an agonistic antibody.

It attaches to the CD137 receptor’s membrane proximal epitope, which will result in the improved activation of T-Cells and NK Cells.

In a Phase I dose escalation and cohort expansion study, CTX-471 demonstrated to be well-tolerated.

The Phase Ib monotherapy study is completely enrolled and underway. CTX-471 has been assessed in this trial in patients with advanced solid tumours who received a minimum of one checkpoint inhibitor post progression.