Radiopharm Theranostics extends access to Terbium-161 to treat advanced prostate cancer

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By Imelda Cotton - 
Radiopharm Theranostics ASX RAD 402 TerThera Terbium-161 treat advanced prostate cancer Tb-161

Radiopharm Theranostics (ASX: RAD) has extended an agreement with Dutch radionuclide producer TerThera for the supply of Terbium-161 (Tb-161) in the development of lead candidate RAD402 to treat advanced prostate cancer.

The agreement is for an initial period of three years and Radiopharm is expected to place an initial order for the isotope later this year.

Tb-161 will be linked to a proprietary monoclonal antibody (mAb) to form Radiopharm’s RAD402 radiotherapeutic designed to target the KLK3 gene which is highly expressed in prostate cancer cells but limited in healthy tissue.

Radiopharm plans to initiate a Phase I dose escalating trial evaluating the safety and efficacy of the novel radiopharmaceutical in late 2024.

Differentiated technology

Managing director Riccardo Canevari said the company was keen to bring a highly differentiated technology such as Tb161-RAD402 to patients with advanced prostate cancer.

“Until now, prostate-specific membrane antigen (PSMA) targeting agents have represented the only theranostic option in the market or in development [but] we have decided to leverage a different mechanism of action by targeting KLK3… the combination with Tb-161 is unique and highly promising,” he said.

“We signed our first agreement with TerThera in April for RAD602 in brain cancer and we have now decided to develop a second molecule linked with Tb-161… we are the first company with access to Tb-161 for clinical development [and] it is a really exciting innovation.”

Strong pre-clinical results

Tb-161 has shown strong pre-clinical results in comparison with the predominantly-used Lutetium 177 (Lu-177) targeted radiation therapy.

It is believed to be ideal for targeted cancer treatment due to its unique emissions of Auger electrons and short-range beta particles.

The beta radiation travels only a few millimetres and Auger electron emission has a higher linear energy transfer which travels less than the width of a single cell.

The Auger effect increases the potency and efficacy of selective tumour cell destruction while leaving surrounding healthy tissue largely unaffected.

Mr Canevari said Tb‐161 had shown excellent bio-equivalence, presenting a bio-distribution comparable to current radiolanthanides and is “potentially superior” to Lu-177.

It is expected to translate into higher absorbed doses in micro-metastatic disease, with less kidney toxicity.