Study of Proxinium for Treating Patients With Squamous Cell Head and Neck Cancer

This study was an open-label, multicentre, dose determination study evaluating the safety and tolerability of Proxinium in the treatment of patients with advanced SCCHN who had received at least one anti-cancer treatment regimen for advanced disease. Fifteen patients were enrolled at nine sites. All patients with histologically confirmed SCCHN who had advanced disease were considered potential candidates for study entry.

Patients completed two phases of screening termed Initial Screening and Final Screening. Initial Screening assessed the EpCAM status of the patient's SCCHN prior to final screening procedures taking place. Patients had to have a biopsy of their advanced disease that had been appropriately collected for verification of EpCAM-positive SCCHN by immunohistochemical methods. If EpCAM-positive SCCHN was confirmed, the patient could enter Final Screening to determine full eligibility for participation in the study. At the beginning of Final Screening, all patients had to have received at least one anti-cancer treatment regimen for advanced disease. Patients who had successfully completed both Initial and Final Screening had a Principal Target Tumour and up to five additional Target Tumours designated for treatment prior to Day 1 dosing. Only one target tumour per week was to be injected. The Investigator was to treat the principal target tumour until clinically relevant tumour control of the principal target tumour was achieved, at which point other target tumours could be chosen and injected once per week at the same dose level of Proxinium.

The study was to comprise two stages. In Stage I, the recommended dose (RD) for Proxinium was to be determined based on the rate of dose-limiting toxicities (DLTs) within each dose cohort. A DLT was defined as the occurrence of excessive toxicity during the first four weeks of each patient's treatment with Proxinium during Stage I of the study, before the RD had been determined. The RD was to be established as the highest dose at which one or fewer patients out of six within a dose cohort experienced a DLT. The initial dose level was to be 500 µg, and three patients were to be initially enrolled into this dose cohort.

Doses were to be escalated to a maximum of 700 µg or de-escalated to a minimum of 260 µg according to the prescribed algorithm outlined in the study protocol and based on the number of patients experiencing a DLT within each dose cohort. Safety data was to be reviewed by the medical monitor, the site investigators who had enrolled patients at that dose, and Viventia Biotech Inc. (the sponsor) to determine if escalation or de-escalation was to occur. All Stage I patients, including those in the original RD cohort, were to remain in Stage I and continue treatment beyond their initial four weeks at their original dose assignment. If dose de-escalation was deemed necessary, all Investigators with patients receiving higher doses would have been notified and given the option of either administering a de-escalated dose or discontinuing treatment.

Stage II was to commence once the RD had been determined and an independent third party had reviewed the safety data. Patients enrolled subsequently were to receive treatment at the RD.

The RD cohort was to be expanded to include a total of 15 patients, and safety and efficacy evaluation was to continue being assessed.

Continued safety and tolerability as well as response rates, therapeutic endpoints, survival time, PK parameters, and immunogenicity were evaluated. Regardless of dose cohort, all patients were to be treated until complete resolution of all accessible Target Tumours, clinically relevant tumour progression, or until study drug suspension or withdrawal criteria had been met.

Four weeks after the end-of-treatment visit, patients were to return to the site for a follow-up visit that was to include a CT scan of the head and neck as well as other assessments, as described in the study protocol. Subsequently, patients were to enter the post-study surveillance period.

Enrolment in the study was halted before the RD of Proxinium was determined, and hence, Stage II of this study was not conducted.