To evaluate the feasibility of inserting Tutelix™ to reduce the dose of radiation to the rectum in men undergoing radiotherapy.

The Tutelix solution will be inserted transperineally under Transrectal Ultrasound (TRUS) guidance between the prostate and the rectum prior to radiotherapy. Tutelix is a water-based solution of a proprietary synthetic polymer with rheological characteristics similar to water, it is radiologically opaque, ensuring safe, simple, and effective administration. This solution can be injected through a fine gauge needle and forms a cohesive hydrogel matrix upon administration. The gelation is triggered by physiological temperature and does not involve any polymerisation or chemical reaction. The resulting hydrogel matrix is self-moulding as it sculpts with itself to form a consistent, homogenous and cohesive structure which can be viewed clearly under ultrasound imaging. This facilitates pinpoint visualization of the investigational device during its administration as it is molded into the optimal position. The main component of the Tutelix investigational device is a proprietary polymer (PPHO). This polymer is the second generation of the PNPHO polymer, developed and clinically tested by Tetratherix Technology Pty Ltd for dental applications under (PET-A, HREC/16 SVHM 258, PET-B, HREC 043/19) and currently under investigation for dermal applications (TD-SI-001, HREC 288/23). PNPHO and PPHO are both dissolved in buffered solutions, which are 95% similar in terms of chemical/ molar composition and have identical mode of action and thermoresponsive properties. It is a prospective, first-in-human, single arm study, of up to 15 participants pre-planned to receive 60Gy in 20 fractions as part of definitive RT for prostate cancer. involving two stages. Cohort 1: up to 3 participants will receive IP containing 40 mg/ml iohexol. Cohort 2: Up to twelve participants will receive the IP containing 40 mg/ml or 160 mg/ml iohexol. This stage will begin after a Safety Review Meeting (SRM) from stage 1 has occurred and the Safety Review Committee (SRC) has voted to proceed to further enrol in the study. The Tutelix will be administered by a radiation oncologist or urologist with extensive experience in prostate rectal spacers. The injection of the Tutelix takes 1-2 minutes. The total procedure time is 15-20 minutes including preparation time. 15-20 mls of the solution is administered, this is at the discretion of the proceduralist, given the different anatomical variations such as size of prostate and position of rectum as this varies. Preclinical studies indicate the Tutelix hydrogel remains in the body for 6 months, this is a secondary endpoint of the study. Review of medical records and procedural surveys will be used to monitor adherence to the intervention. Stage 1 duration will be less than 3 months. Stage 2 will commence after the safety review meeting for stage 1, which will be approximately 28 days after stage 1. The duration of Stage 2 is 12 months.