CTX-009 Shows Preliminary Activity/Safety in Biliary Tract Cancer

In patients with biliary tract cancer (BTC), treatment with CTX-009 (ABL001) in combination with paclitaxel demonstrated preliminary efficacy and tolerable safety, according to interim analysis findings from a phase 2 study (NCT04492033).¹

Result announced in a press release by Compass Therapeutics, Inc revealed a 42% overall response rate consisting of 10 partial responses (PRs) in the population of 24 patients.

“We are excited by these impressive interim phase 2 results and believe CTX-009 is a promising investigational drug. In the initial data review of this trial, reported in November 2021, CTX-009 exhibited a 29% ORR and a 100% CBR. We are very encouraged by the performance of CTX-009 across a larger patient population, particularly the maturing of the dataset, with the ORR moving from 29% in 17 evaluable patients to 42% in all 24 patients enrolled, stated Thomas Schuetz, MD, PhD, chief executive officer, and scientific founder of Compass, in a press release.

The phase 2, prospective, multi-center, open-label study of CTX-009 in patients with BTC has a phase 2 primary end point of ORR, and secondary end point including the severity of adverse events (AEs), pharmacokinetics, ORR, disease control rate, time to treatment failure, progression-free survival, survival rate, and overall survival.^1,2

The study follows a Simon’s 2-stage adaptive design. With this design, the first 21 patients who achieved a PR will be advanced to the second stage of the study. Prior to the interim analysis, it was reported that CTX-009 achieved 5 PRs in the study population, which at the time included 17 evaluable patients.

Patients enrolled to the study were those with intrahepatic cholangiocarcinoma (37.5%), extrahepatic cholangiocarcinoma (12.5%), gallbladder cancer (29.2%) and ampullary cancer (20.8%). Baseline characteristics showed that 45.8% of the patients received 1 prior therapy and 54.2% of the patients received at least 2 prior therapies. The majority of study subjects (95.8%) received gemcitabine/cisplatin. The median age of patients in the study was 61.5 year, and the cohort had an ECOG performance status of 0 (54.2%) or 1 (45.8%).

Those included have received at least 1 dose of CTX-009 plus paclitaxel as of the data cutoff date of April 14, 2022. Safety results showed that all patients experienced at least 1 AE. The most common any-grade AEs were anemia (12.5%), asthenia (25.0%), fatigue (16.7%), edema (16.7%), pyrexia (16.7%), neutropenia (54.2%), thrombocytopenia (20.8%), headache (16.7%), proteinuria (20.8%), dysphonia (12.5%), dyspnea (25%), epistaxis (33.3%), pulmonary hypertension (16.7%, all Grade 1) and hypertension (50.0%).¹

Grade 3 or higher treatment-emergent adverse events (TEAE) were also observed in the study. The most common high-grade TEAE were neutropenia (50.0%), hypertension (16.7%), anemia (12.5%) and thrombocytopenia (8.3%). All TEAEs were considered manageable.

The study is ongoing at multiple sites in Korea. Recently, an investigational new drug application was opened with the FDA to bring investigations of CTX-009 to patients in the United States (US). The first US patients is expected to be dosed with CTX-009 in the third quarter of 2022.

“CTX-009 demonstrated responses across all of the 4 BTC subtypes enrolled in the trial and good overall tolerability. These are very encouraging aspects of the phase 2 results and mark an important step forward in the ongoing development of CTX-009 as a potential new treatment for patients with BTC. We look forward to studying CTX-009 further in phase 2 trials, which we expect to begin in the US in the third quarter,” said Vered Bisker-Leib, PhD, president and chief operating officer of Compass, in a statement.

_REFERENCES:

_{1. Compass Therapeutics reports positive interim phase 2 data of CTX-009 in combination with paclitaxel in biliary tract cancers. News release. May 4, 2022. Accessed May 6, 2022. https://bit.ly/3Fmlgcq}

_{2. A study of ABL001 in combination with irinotecan or paclitaxel in patients with advanced or metastatic solid tumors. Clinicaltrials.gov. Updated August 12, 2021. Accessed May 6, 2022. https://bit.ly/3FktkKS}