Avacta Group Regulatory News (AVCT)

Faridoxorubicin (AVA6000) Phase 1b cohort demonstrates clinically meaningful tumor shrinkage in patients with salivary gland cancers

Preliminary Phase 1b data is in line with Phase 1a data reported at the European Society of Medical Oncology in September 2025

Combined disease control rate of 90% across both Phase 1a and Phase 1b patients with confirmed partial and minor responses observed

LONDON and PHILADELPHIA - December 17, 2025 - Avacta Therapeutics (AIM: AVCT), a clinical stage biopharmaceutical company developing pre|CISION®, a tumor-activated oncology delivery platform, today announced compelling new data in patients with salivary gland cancer (SGC) enrolled in the ongoing Phase 1b trial of faridoxorubicin (AVA6000). The data show confirmed partial and minor responses, consistent with data previously reported from the Phase 1a part of the study.

Faridoxorubicin is the first peptide drug conjugate (PDC) in Avacta's pipeline. It consists of doxorubicin conjugated with Avacta's proprietary pre|CISION® peptide and is specifically cleaved (released) by fibroblast activation protein-alpha (FAP), which is over-expressed in the tumor microenvironment, enabling targeted release of the doxorubicin payload.

SGC accounts for 6-8% of head and neck cancers, with approximately 2,500 cases diagnosed in the U.S. each year.1 SGC is a disease that does not respond to chemotherapy, has no standard therapy defined in the metastatic setting and a five-year survival rate of approximately 42%2 in advanced stage disease. 

Avacta's recent data demonstrate continued robust and meaningful tumor shrinkage in patients with SGCs and a combined disease control rate of 90% across Phase 1a and Phase 1b patients.

Based on the preliminary favorable efficacy and safety data observed in the Phase 1b cohort in this part of the trial, enrollment will continue in this cohort with further data updates across the Phase 1a and Phase 1b cohorts expected in 1H 2026.

Christina Coughlin MD, PhD, CEO of Avacta, commented:

"These data continue to reinforce our belief in the transformative potential of our pre|CISION® peptide drug conjugates to expand the therapeutic index and increase the efficacy of highly potent therapeutics and further strengthens our confidence across our broader pipeline.

"SGC cancer is a devastating disease with no established standard of care treatment options. The clinically meaningful tumor shrinkage and prolonged progression free survival we have observed in the study highlight faridoxorubicin's potential as an important new treatment option for patients with SGC and other solid tumors. The Phase 1b data will mature as we continue to collect the survival data in this cohort.

"Translational data collected from this population continue to demonstrate the power of our pre|CISION® platform, with optimal payload release observed even at the lowest levels of FAP expression. This supports a broad market opportunity for all pre|CISION® medicines across our pipeline."

Faridoxorubicin (AVA6000) - Clinical data observations in SGC

These data demonstrate ongoing evidence of durable anti-tumor activity in patients with SGC (both treatment-naïve and those who have failed earlier lines of therapy), that is supported by ongoing RECIST3 responses (both partial and minor responses) and continued observation of a robust disease control rate and strong progression-free survival (PFS) data. The trial enrolled both a Phase 1a cohort (n=11) and Phase 1b cohort to date (n=19 evaluable for efficacy) for a total of 30 patients with SGC.

Of the 30 patients with SGC treated at the dose of 250 mg/m2 and above and evaluable for efficacy, nine experienced clinically meaningful disease shrinkage, including two confirmed partial responses (PR, >30% tumor shrinkage) and seven minor responses (MR, >10% and <30% tumor shrinkage) using RECISTv1.1 criteria. PFS in the Phase 1b cohort has not been reached with a median follow up exceeding 15 weeks at the data cutoff.

These data include the following:

· Nineteen patients in the Phase 1b arm of the trial are evaluable for efficacy. Safety findings (n=22) are in line with those data reported in the Phase 1a cohort. Three patients enrolled were not evaluable for efficacy at the data cutoff (2 patients not eligible and 1 patient not having reached an initial follow up scan) but having received one dose of drug are considered evaluable for safety

· The baseline characteristics of the patients enrolled in the Phase 1b are in line with the patients in Phase 1a. In Phase 1b, the median number of prior therapy regimens in the metastatic setting is 1 with a range of 0-2. Seven patients in Phase 1b had not received prior systemic therapy

· Among the total of 30 patients evaluable for efficacy treated at the dose of 250 mg/m2 and above in Phase 1a and 1b, 27 patients demonstrated partial or minor responses or stable disease, resulting in a disease control rate of 90% across the two arms in line with previously reported data

· Clinically meaningful tumor shrinkage was observed with two patients with confirmed partial responses and seven patients with confirmed minor responses (across Phase 1a and 1b)

· Median progression free survival in the cohort of 19 patients in the Phase 1b has not been reached. Thirteen of 19 patients remain on therapy and an additional two patients remain in PFS follow-up at the data cutoff

Although the Phase 1b data are early in the treatment course of most patients, the emerging data are consistent with the previously reported Phase 1a observations with no diminution of activity observed in SGC. Faridoxorubicin continues to demonstrate the favorable safety profile and efficacy in SGC that has characterized it since its initial clinical evaluation.

1 Key Statistics in Salivary Gland Cancers (2025) | American Cancer Society. Available at: www.cancer.org/cancer/types/salivary-gland-cancer.html

2 Survival rates for salivary gland cancer: Salivary gland survival (2025) Salivary Gland Survival | American Cancer Society. Available at: https://www.cancer.org/cancer/types/salivary-gland-cancer/detection-diagnosis-staging/survival-rates.html

3 Reduction in the sum of longest diameters (SLD) is used to measure response per RECIST 1.1 with partial responses having at least a 30% reduction and minor responses of between >10% and <30% reduction.

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About Avacta - www.avacta.com

Avacta Therapeutics is a clinical-stage life sciences company expanding the reach of highly potent cancer therapies with the pre|CISION® platform. pre|CISION® is a proprietary payload delivery system based on a tumor-specific protease (fibroblast activation protein or FAP) that is designed to concentrate highly potent payloads in the tumor microenvironment while sparing normal tissues.

Our innovative pipeline consists of pre|CISION® peptide drug conjugates (PDC) or Affimer® drug conjugates (AffDC) that leverage the tumor-specific release mechanism, providing unique benefits over traditional antibody drug conjugates.

The pre|CISION® platform comprises an anticancer payload conjugated to a proprietary peptide that is a highly specific substrate for fibroblast activation protein (FAP) which is upregulated in most solid tumors compared with healthy tissues. The pre|CISION® platform harnesses this tumor specific protease to cleave pre|CISION® peptide drug conjugates and pre|CISION® antibody/Affimer® drug conjugates in the tumor microenvironment, thus releasing active payload in the tumor and reducing systemic exposure and toxicity, allowing dosing to be optimized to deliver the best outcomes for patients.