Preliminary evaluation of the safety and feasibility of toll-like receptor ligand CB101 combined with hypofractionated radiation therapy in canine head and neck cancer: a pilot study

Radiation therapy (RT) is a common treatment modality for dogs with locally advanced head and neck tumors. Most dogs experience a clinical benefit secondary to RT, however, long term remissions are rare. This study evaluates the feasibility and safety profile of intratumoral CBC101 (a proprietary hydrogel-based injectable resiquimod formulation), a toll-like receptor (TLR) 7/8 agonist with immunomodulatory properties, when used in combination with radiation therapy. Three dogs with histologically confirmed head/neck cancers were prospectively enrolled. A baseline CT scan was performed. Dogs received palliative radiation therapy (8 Gy × 4) in conjunction with intratumoral CB101. A follow-up CT scan was performed at week 12 to assess tumor response and to evaluate for metastatic disease. Intratumoral CB101 was well-tolerated, feasible, and produced minimal adverse effects. Only one grade 1 adverse event was attributable to CB101; all other adverse events were expected radiation therapy side effects. The data obtained from this preliminary study will be used for further investigation into appropriate dosing and timing of intratumoral resiquimod or other TLRs, with eventual escalation into phase II and III clinical trials.