On May 25, 2023 Theratechnologies Inc. ("Theratechnologies" or the "Company") (TSX: TH) (NASDAQ: THTX), a biopharmaceutical company focused on the development and commercialization of innovative therapies, reported preliminary efficacy data from a Phase 1 study of its lead investigational peptide-drug conjugate (PDC) candidate, sudocetaxel zendusortide (formerly TH1902), in patients with advanced solid tumors (Press release, Theratechnologies, MAY 25, 2023, View Source [SID1234632080]). In a June 3 poster session at the 2023 annual meeting of the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) in Chicago, researchers will present early results from Part 1 (dose escalation) and Part 2 (dose expansion) of the multicenter, open-label trial of sudocetaxel zendusortide, in which 36% of heavily pretreated participants experienced a clinical benefit, including two patients with partial responses (PR) and seven achieving prolonged stable disease (SD).

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Based on the results presented at ASCO (Free ASCO Whitepaper), Theratechnologies is engaged with the U.S. Food and Drug Administration (FDA) to amend the protocol of the Phase 1 clinical trial of sudocetaxel zendusortide. The amendments are designed to improve the therapeutic window and allow for more prolonged therapy with sudocetaxel zendusortide, reflecting changes in patient selection and evaluation of alternative dosing regimens.

"The early efficacy data for our lead peptide-drug conjugate, sudocetaxel zendusortide, confirm that it rapidly internalizes and hyper-targets delivery of cytotoxic payload directly into cancer cells," said Christian Marsolais, Ph.D., Senior Vice President and Chief Medical Officer at Theratechnologies. "We look forward to re-initiating our trial with a revised protocol that increases the likelihood of showing the full therapeutic potential of sudocetaxel zendusortide."

"These preliminary data on safety and antitumor activity have informed the proposed changes to the protocol, with the intention of improving the risk-benefit profile of sudocetaxel zendusortide in the next stage of the trial," commented lead investigator Funda Meric-Bernstam, M.D., Chair of the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center.

Study details and results

Part 1 of the study enrolled 18 adults with a confirmed diagnosis of a metastatic or advanced-stage solid tumor that is refractory to standard therapies (average of 8 prior lines of therapies). The starting dose of 30 mg/m2 every 3 weeks (Q3W) was selected based on sudocetaxel zendusortide preclinical data. Among participants in Part 1, one patient with endometrial cancer experienced SD for 233 days (33 weeks), a second patient with prostate cancer had SD that lasted for 119 days (17 weeks), and a third patient with ovarian cancer experienced SD for 295 days (42 weeks).

Eighteen additional patients were enrolled into the 300 mg/m2 Q3W dose expansion cohort (Part 2). In an interim efficacy and safety analysis of the 300 mg/m2 dose cohort from Parts 1 and 2 (n=25), five of six patients (83%) with ovarian cancer had a best overall response (BOR) of either PR (n=1) or SD (n=4). In the triple-negative breast cancer (TNBC) population, three of four patients (75%) had a BOR of SD, with one patient experiencing SD for at least four cycles and continued clinical benefit up to at least 24 weeks. In the two patients with prostate cancer, one experienced a PR.

Sudocetaxel zendusortide doses below 300 mg/m2 were well-tolerated in Part 1 of the trial, which established the maximum tolerated dose (MTD) and dose-limiting toxicities at 360 mg/m2 and 420 mg/m2, respectively. Based on those results, investigators selected a 300-mg/m2 dose for Part 2 (dose expansion) of the basket trial, to determine the safety and efficacy of sudocetaxel zendusortide in patients with multiple tumor types with high expression of the sortilin (SORT1) receptor. At 300 mg/m2, the most common treatment-related adverse events (>20%) were ocular changes, neuropathy, gastrointestinal disturbances, and musculoskeletal complaints, with Grade 3 or greater toxicities at a frequency of ≤12%.

Poster presentation details:

Title: "Sudocetaxel zendusortide (TH1902), a novel sortilin-receptor (SORT1)-targeting peptide-drug-conjugate (PDC) in patients (pts) with advanced solid tumors: Results from part 1 (dose-escalation) of a phase 1, open-label study"

Lead author: Funda Meric-Bernstam, M.D., Chair of the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center

Abstract number: 3089

Session Date and Time: Saturday June 3, 2023, Developmental Therapeutics – Molecularly Targeted Agents and Tumor Biology, 8:00-11:00 CDT

About SORT1+ Technology and Sudocetaxel Zendusortide (TH1902)

Theratechnologies has established its SORT1+ TechnologyTM platform as an engine for the development of proprietary peptide-drug conjugates (PDCs) that target the sortilin (SORT1) receptor, which is expressed in multiple tumor types. SORT1 is a "scavenger" receptor that plays a significant role in protein internalization, sorting, and trafficking. Expression of SORT1 is associated with aggressive disease, poor prognosis, and decreased survival. It is estimated that SORT1 is expressed in 40% to 90% of endometrial, ovarian, colorectal, triple-negative breast (TNBC), and pancreatic cancers, making this receptor an attractive target for anticancer drug development.

Sudocetaxel zendusortide is the first-of-its-kind SORT1-targeting PDC, and the first to emerge from the SORT1+ Technology platform. A new chemical entity, sudocetaxel zendusortide employs a cleavable linker to conjugate (attach) a proprietary peptide to docetaxel, a well-established cytotoxic chemotherapeutic agent used to treat many cancers. The FDA granted Fast Track designation to sudocetaxel zendusortide as a single agent for the treatment of all sortilin-positive recurrent advanced solid tumors that are refractory to standard therapy. Sudocetaxel zendusortide is currently being evaluated in a Phase 1 clinical trial. Patient recruitment was voluntarily paused on December 1, 2022, and in alignment with this decision, the FDA placed the trial on partial clinical hold. In May 2023, the Company submitted a proposed protocol amendment to the FDA that is currently under review.