Avacta Therapeutics presents compelling Phase 1a data for faridoxorubicin and the pre|CISION^® platform at the European Society of Medical Oncology Annual Congress

Median progression free survival (PFS) has not been reached in the cohort of patients with salivary gland cancer with PFS follow up suggesting a more than doubling of the benchmark PFS and a disease control rate of 91%

No maximum tolerated dose reached despite dosing up to 385 mg/m² (approximately 4x conventional doxorubicin dose) with no severe cardiac toxicity observed even at cumulative doses up to 550 mg/m²

LONDON and PHILADELPHIA - October 20, 2025 - Avacta Therapeutics (AIM: AVCT, 'Avacta', 'the Company'), a clinical stage biopharmaceutical company developing pre|CISION^®, a unique oncology delivery platform, today announces further development updates in the Phase 1a clinical trial with its lead program, faridoxorubicin (FAP-Dox, AVA6000) were presented at the 2025 European Society of Medical Oncology Annual Congress in Berlin, Germany on October 19, 2025.

Faridoxorubicin treatment data demonstrate favorable safety and tolerability across both the every three weeks and every two weeks dosing regimens. The trial data also demonstrate a robust reduction in toxicities associated with conventional doxorubicin therapy, with preliminary efficacy in patients with salivary gland cancers and soft tissue sarcomas. Cardiac safety data in patients treated above the standard cumulative dose demonstrate no severe toxicity observed either in treatment stage or in follow up and no severe cardiac adverse events were reported in the trial, regardless of the cumulative dose level.

Median progression-free survival (PFS) has not been reached in the previously-reported cohort of patients with salivary gland cancers, indicating a durable response. The follow up data to-date suggest a duration of PFS that is more than double the duration of that reported in benchmark data in this patient population of pretreated patients in Phase 1a (median duration of PFS follow-up of 41 weeks).

Christina Coughlin, CEO Avacta commented:

"We are delighted to confirm the observations first published in April of this year with exciting efficacy in patients with salivary gland cancers. These data continue to demonstrate the power of pre|CISION^® to generate meaningful PFS data in a patient population with limited therapeutic options and importantly with no FAP on the tumor cells.

"Given the extension of PFS, we are excited to be moving this program forward. The very strong cardiac safety data out to the cumulative maximum dose of 550 mg/m² validates the safety implications of the platform and has the potential to open up a new avenue of treatment options for patients.

"These data highlight three important findings for the pre|CISION^® platform: first, the elimination of the cardiac signal even at higher cumulative doses demonstrates that pre|CISION^® is capable of protecting normal tissues from toxicity. Second, the activity in a tumor type without FAP on the tumor cells confirms the bystander effect of pre|CISION^® and third, the tumor concentration data even at low FAP expression opens up an even greater number of cancer types to the platform.

"This development, combined with the recent update on our first dual payload peptide drug conjugate, underscores the tremendous potential of our proprietary pre|CISION^® technology pipeline to deliver meaningful benefits for patients."

Faridoxorubicin (AVA6000, FAP-Dox) Clinical Highlights (ESMO Developmental Therapeutics Poster Session, October 19, 2025)

Faridoxorubicin is a FAP-activated form of doxorubicin designed to reduce the systemic side effects of conventional chemotherapy and concentrate the active payload in the tumor microenvironment. Prior reports (AACR Annual Meeting, April 2025) have demonstrated favorable preliminary safety and early efficacy data in a subset of patients with salivary gland cancers.

Clinical data with faridoxorubicin

In the Phase 1a dose-escalation study, faridoxorubicin was well-tolerated across both every-three-week (Q3W) and every-two-week (Q2W) dosing regimens (N-63 patients). No maximum tolerated dose (MTD) was reached despite dosing up to 385 mg/m² every three weeks. In addition, no events of severe cardiac toxicity were observed even to maximum cumulative exposure consistent with the anthracycline dose of 550 mg/m², further supporting a markedly improved safety profile over conventional doxorubicin.

In patients with salivary gland cancers (SGC, n=11) treated at or above the dose level of 250 mg/m², faridoxorubicin demonstrated multiple confirmed partial and minor responses with a disease control rate of 91%. Median progression-free survival (PFS) has not yet been reached, with an absolute median PFS follow-up of approximately 41 weeks (range 8 to 76 weeks). Multiple patients demonstrate durable disease stabilization despite discontinuing the therapy once reaching the cumulative maximum dose. The Kaplan Meier estimated median follow-up is 51 weeks. Kaplan Meier modeling functions by calculating the probability of overall survival at each event time and multiplying these probabilities to estimate the median follow up based on observed data. The faridoxorubicin observations compare favorably to recent benchmarking data in this patient population presented at ESMO 2024, with a reported PFS of 3.5-4 months in a large cohort (n=54) published by the EORTC in a similar setting of pretreated patients with SGC. In addition to the comparison to the pretreated patient cohort,, the data with faridoxorubicin compare well to the first line cohort in this EORTC study, with a PFS reported at 4-6.5 months (Licitra et al. ESMO Annual Congress 2024).

In patients with soft tissue sarcomas (n=17 evaluable), multiple tumor responses are observed, even at lower doses including one responder at the 160 mg/m² Q3W dose level. The stabilization of disease despite the removal of the drug is observed in this indication as well, suggesting a highly-effective and durable treatment in this cancer indication. The key difference between the biology of many subsets of soft tissue sarcoma and other epithelial malignancies is that many sarcoma subsets demonstrate direct tumor cell expression of FAP, which could enhance efficacy. The vast majority of epithelial malignancies do not demonstrate expression of FAP on tumor cells, only on the cancer associated fibroblasts.

Cardiac safety data demonstrate that despite dosing of faridoxorubicin with a cumulative exposure up to 550 mg/m² of conventional doxorubicin, no severe cardiac events were reported, either during the dosing timing or in the follow-up period. Echocardiogram (ECHO) data were analyzed similar to the liposomal doxorubicin label in the full cohort of patients and these data presented based on the cumulative dose received of released doxorubicin. These data reveal that only two patients demonstrated ECHO changes consistent with adverse findings, one patient treated below the maximum of 450mg/m² and one patient treated to 500 mg/m². This includes a patient reported previously experiencing the early dose limiting toxicity due to ECHO changes in the 120 mg/m2 Q3W cohort (grade 2 cardiac failure). None of the patients treated to the cumulative dose of 550 mg/m² demonstrated observed ECHO changes. The cardiac safety data compare favorably to that reported with both the doxorubicin and liposomal doxorubicin respective drug labels.

Clinical pharmacology data with faridoxorubicin

Despite dosing up to approximately 4x the dose of conventional doxorubicin, the data demonstrate exposure of released doxorubicin in plasma and normal tissues is generally lower than that observed with conventional dose doxorubicin (75 mg/m² Q3W) and the median tumor to plasma ratio is 100:1. The lack of toxicity is explained by the limited tissue distribution as well as limited first pass effect exposure of released doxorubicin (reported in Lahu et al. AACR 2025).

Biopsy and plasma data collected during the trial at 24 hours after the first dose demonstrate two key factors relevant to the pre|CISION^® platform: (1) intratumoral concentration of the active payload is dose-dependent, indicating that the higher doses lead to higher absolute values of released doxorubicin in the tumor and (2) efficient cleavage of the PDC is observed in all tumors, even those with limited 1+ expression, suggesting the lower level of expression required for cleavage of the peptide is quite low, demonstrating the potential of pre|CISION^® medicines in a number of other malignancies with lower expression of FAP.

Avacta continues to enroll patients in the Phase 1b expansion cohorts with data in salivary gland cancer anticipated by the end of 2025. 

Title: A Phase I trial of FAP-Dox (AVA6000), a Fibroblast Activation Protein (FAP)-released and tumor microenvironment (TME)-targeted doxorubicin peptide drug conjugate in patients with FAP-positive solid tumors

Session Title: Developmental Therapeutics

Session Date and Time: 17 October, 19:40 - 20:00

Location: Berlin Auditorium - Hub 27

Abstract Presentation Number: 964P

Speaker: William D. Tap

Avacta will present an Investor Meet conference to review the published data on Tuesday October 21, 2025.  Details for the webinar will be posted on the Avacta home page. 

Lahu G., et al. (2025). Comparative Pharmacokinetics and Tumor Activation of Fibroblast Activation Protein (FAP)-enabled pre|CISION® Peptide Drug Conjugates.  AACR Annual Meeting, abstract CT15.

Licitra et al. (2024). A randomised phase I study to evaluate the efficacy and safety of androgen deprivation therapy (ADT) vs chemotherapy (CT) in patients with recurrent and/or metastatic, androgen receptor (AR) expressing, salivary gland cancers. ESMO Annual Congress, abstract LBA36.

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For further information from Avacta, please contact:

About Avacta - www.avacta.com

Avacta is a clinical stage life sciences company developing an innovative proprietary drug delivery peptide drug conjugate (PDC) platform, pre|CISION^®. The pre|CISION^® platform uniquely enables the repurposing of a range of oncology drugs as PDC payloads with the goal to significantly reduce toxicity and side effects for patients by concentrating the drug directly in the tumor.

About pre|CISION^®

The key aspect of pre|CISION^® is its peptide drug conjugates (PDC) technology. The combination of the cancer drug and the proprietary cleavable peptide (the PDC) is inert and incapable of entering cells and killing them until the peptide is specifically released within the tumor. The active payload in the pre|CISION^® PDC is released when the PDC comes into contact with the common tumor-associated protein, known as fibroblast activation protein (FAP), in the tumor. The release of the payload from the pre|CISION^® product directly in the tumor results in higher concentration of the drug at the tumor and lower blood and healthy tissue levels than standard systemic administration, offering the potential to improve efficacy and patient tolerability.