Responses observed in patients with very low FAP expression with persistence of FAP expression observed despite tumor response
Further data updates expected in Q3 2026
LONDON and PHILADELPHIA – June 25, 2026 – Avacta Therapeutics (AIM: AVCT, “the Company”, “Avacta”), a clinical stage biopharmaceutical company developing pre|CISION®, a tumor-activated oncology delivery platform, today announces platform-validating data with faridoxorubicin (AVA6000, pre|CISION®-enabled doxorubicin) in patients with salivary gland cancer (SGC) where robust tumor responses are observed with low expression of fibroblast activation protein (FAP) and the persistence of FAP expression despite tumor response.
Christina Coughlin, CEO of Avacta, commented:
“The latest data with faridoxorubicin further validate the potential of our pre|CISION® platform to create products which can significantly improve treatment options for cancer patients. The activity in patients with minimal FAP expression, as well as persistence of FAP despite robust tumor reduction, underscore the potential of the platform in multiple malignancies with additional payloads.
“We are pleased to see that median progression-free survival is not yet mature in the SGC cohort as this may suggest that our pre|CISION®-enabled doxorubicin is controlling tumor growth in these patients as effectively as we initially observed in the Phase 1a cohort”.
Clinical data updates
Responses were reported from two of the patient cohorts studied, SGC and soft tissue sarcoma (STS). In the lead indication of SGC, the data continues to mature.
The patient population in SGC (n=32) is the most mature data set from the trial and is used to assess the efficacy endpoints. Patients in this cohort were selected based on the agreed population for the pivotal study in this indication, where more rare subsets of SGC were excluded based on differing natural histories which can be challenging to control for in a trial with PFS as the primary endpoint. Previously, Avacta has reported data in the full cohort of SGC (n=38), this announcement today includes efficacy data in the subset as defined in the patient population for the pivotal study. Patients in this cohort (n=32) were assessed for best overall response with four confirmed partial responses, and eight confirmed minor responses (sum of the longest diameters -10 to -29%). Median progression-free survival data are not yet mature in this cohort, as progression events (tumor growth, etc.) continue to be collected and overall survival data continue to mature. Tumor responses are also observed in the STS cohort, where importantly, tumor cells have expression of FAP. The cohort of triple negative breast cancer continues and data will be reported when mature.
The robust clinical activity observed in both STS and SGC patient populations demonstrates the efficacy of faridoxorubicin even when FAP is only expressed in the stromal cancer associated fibroblasts (CAFs), thus validating the “bystander effect” of pre|CISION®. In STS, FAP expression is seen on the surface of tumor cells, whereas FAP is absent on SGC tumor cells, which is representative of the majority of solid tumor indications.
These updates further support the Board’s belief that Avacta’s pre|CISION® technology is broadly applicable across multiple cancer indications.
Translational findings in SGC
Together, translational findings from biopsy and FAPI-PET imaging data indicate two key features of the platform:
- pre|CISION® medicines can have optimal activity even in the setting of very low FAP expression.
- The expression of FAP in tumors persists, despite robust and durable tumor response.
To assess the activity of faridoxorubicin in patients with low expression of FAP, biopsy data in the full SGC cohort were available in n=26 patients and were assessed with standard FAP immunohistochemistry and tri-color immunofluorescence studies. Two different statistical analyses both demonstrate no relationship between the level of FAP expression and degree of tumor response. Importantly, these analyses and the case series presented (n=4 responders) show that the activity of faridoxorubicin in SGC is robust even to a very low level of FAP expression.
The changes in the expression of FAP over time with faridoxorubicin therapy have been assessed in a sub-study of the Phase 1a/1b using FAP inhibitor (FAPI)-PET scanning ([18F]FAPI-74). This sub-study allows the monitoring of FAP expression pre- and post-treatment. The preliminary results reported demonstrate that FAP expression in patients with tumor response to AVA6000 is not reduced to the degree of tumor shrinkage (n=2). This key finding shows the rationale for response in patients with lower levels of FAP expression in that FAP is an extracellular enzyme, and cleavage of a pre|CISION® medicine requires no internalization and the enzyme (FAP) continues to be readily available even in the setting of deep response.
The full data release at the BIO International Convention, including details on the translational findings, is available on the Avacta website here.