A first-in-human, phase 1 study evaluating oral TACC3 inhibitor, AO-252, in advanced solid tumors.
Authors: Dumbrava Ecaterina Elena , Kennon Amber Michelle , Balema Wintana A , Lim Chaemin , Vempati Sridhar , Stergiopoulos Sotirios , Richardson Debra L. 
Published: June 2024

TPS3176 Background: TACC3 is the most oncogenic member of the transforming acidic coiled-coil domain-containing protein (TACC) family, which have important roles in microtubule and centrosome-related processes. TACC3 is overexpressed in multiple cancers with centrosome amplification caused by genomic aberrations such as TP53 mutations, leading to chromosome instability and worse prognosis. AO-252 is a computationally designed, small molecule inhibitor of TACC3 protein-protein interactions. Binding assays and kinome screening suggested the specificity of AO-252 to TACC3. AO-252 targets the interactions of TACC3 with Clathrin/KIFC1, BRDA1 and MBD2/HAT complexes regulating mitosis, DNA damage response and epigenetic functions and was confirmed using co-immunoprecipitation (co-IP) assays. Gene expression analysis in multiple cell lines further confirmed the various TACC3 pathways affected by AO-252. In vitro, AO-252 showed low nanomolar potency in >200 cell line panel covering multiple different cancer indications and spared the normal cells. In vivo, AO-252 demonstrated strong tumor growth inhibition or regression in multiple xenograft models including triple-negative breast (TNBC), high-grade serous ovarian (HGSOC) and endometrial cancer with TP53 mutation/loss with a good therapeutic index. Methods: This first-in-human, multicenter, open-label phase I dose escalation and expansion study evaluates the safety, tolerability, maximum tolerated dose, and recommended phase 2 dose (RP2D) of AO-252 in solid tumors (NCT06136884). Patients with unresectable or metastatic TNBC, platinum-resistant HGSOC, primary peritoneal, fallopian-tube and serous endometrial cancers with documented TP53 mutation/loss, who have failed on at least 1 prior line of systemic therapy in advanced/metastatic setting (maximum 4 for TNBC and endometrial carcinoma) are eligible for enrollment. Part 1 follows an accelerated titration dose-escalation for cohort 1 and 2 and a traditional 3+3 study design from cohort 3. A maximum of 54 patients will be treated in the dose escalation, patients receiving AO-252 orally once or twice daily in a 28-day cycle. Part 2 consists of dose-expansion of a maximum of 30 patients into 2 RP2D levels of AO-252. Primary objectives are to evaluate the safety and tolerability as noted by dose-limiting toxicities, adverse events, serious adverse events, laboratory test results, electrocardiograms, vital signs, physical exams, and ECOG performance status. Secondary objectives are to determine the antitumor activity assessed by objective response rate per RECIST1.1, duration of response and disease control rate and to determine the pharmacokinetics of single and repeated doses of AO-252. Potential biomarkers relating to treatment outcome will be evaluated as exploratory endpoints. Enrollment in Cohort 1 is completed and enrollment to Cohort 2 will begin in February 2024. Clinical trial information: NCT06136884 .