What question did this study set out to answer?

This study aims to assess the safety and efficacy of JK06, targeting the 5T4 protein in advanced solid tumors.

April 19, 2026

Abstract CT250: A phase 1b / 2 study of JK06, a 5T4-targeted antibody drug conjugate, in patients with unresectable locally advanced or metastatic cancer

Key Points

This study aims to assess the safety and efficacy of JK06, targeting the 5T4 protein in advanced solid tumors.
Patients with relapsed solid tumors received intravenous JK06 every 3 weeks.
Dose escalation completed, with multiple tumor-specific cohort expansions.
Fresh and archival tumor biopsies were collected for analysis of 5T4 expression.
Response evaluations were conducted every 9 weeks using RECIST v1.1.
Among 69 treated patients, a 38% overall response rate (ORR) was observed in NSCLC with one complete response.
In breast cancer, a 17% ORR was noted with one confirmed partial response.
Most adverse events were low-grade (Gr 1 & 2), with a few Gr 3 events that resolved.
No Gr 4 adverse events recorded; one patient experienced a Gr 5 event of pneumonitis.

Abstract

Abstract 5T4, a Type I transmembrane glycoprotein, has limited expression in normal adult tissues but is over expressed in a broad spectrum of solid tumors. It modulates the CXCR4 and WNT signaling pathways contributing to epithelial to mesenchymal transition and correlates with poorer clinical outcomes among a range of cancers, such as NSCLC, CRC and ovarian. JK06 is a tetravalent, biparatopic DAR2 MMAE ADC targeting 5T4, providing picomolar affinity n = 31 in cohort expansions) have been treated, median age of 61. 5 years and 74% of treated patients have had ≥ 3 prior lines of therapy. Treatment has been well-tolerated with predominantly low-grade treatment-related adverse events (TRAEs) (Gr 1 no Gr 4 JK06-related AEs have been observed to date. Three patients underwent dose reductions, and three additional patients were discontinued due to TRAEs. One patient sustained Gr 5 treatment-related pneumonitis at a higher dose that is not being evaluated in cohort expansion. Among 13 response-evaluable NSCLC patients in dose escalation, a 38% ORR has been observed, with 1 confirmed complete response (cCR) and 4 confirmed partial responses (cPR) (one with CNS response), with the longest continuing therapy for 51 weeks. One of six evaluable breast cancer patients (17% ORR) achieved a cPR and remained on treatment for 27 weeks. To date, JK06 demonstrates promising clinical activity among refractory NSCLC and breast cancer at multiple dose levels while being well tolerated without significant drug-related toxicities. Updated dose escalation data and initial expansion cohort data will be presented. Citation Format: Omar Saavedra, Fabricio Racca, Valentina Boni, Emiliano Calvo, Brant Delafontaine, Sylvie Rottey, Bernd Dekeyser, Hans Prenen, Maria deMiguel, Valentina Gambardella, Lionel d'Hondt, Vladimir Galvao, Judit W. Johnson, Jonathan P. McNally, Jennifer Lindelien, Alice Drumheller, Jijun Dong, Samuel P. Murphy, Shalabh Singhal, Naimish Pandya, Nuria Kotecki. A phase 1b / 2 study of JK06, a 5T4-targeted antibody drug conjugate, in patients with unresectable locally advanced or metastatic cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts) ; 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86 (8Suppl): Abstract nr CT250.

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Discussion

Journals

Cancer Research

Institutions

Ghent University Hospital

Vall d'Hebron Hospital Universitari

Antwerp University Hospital

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