AVA6000

What is AVA6000?

AVA6000 is Avacta Therapeutics' investigational peptide-drug conjugate (PDC) consisting of doxorubicin masked by a fibroblast activation protein (FAP)-cleavable peptide linker. FAP is a serine protease expressed on cancer-associated fibroblasts in the tumor microenvironment, with elevated expression in many solid tumors (sarcoma, breast, pancreatic, others) but minimal expression in healthy tissue. The pre|CISION platform exploits this differential expression: the doxorubicin is biologically inactive until the peptide linker is cleaved by FAP at the tumor site, locally releasing active drug. The strategy aims to deliver the established cytotoxic doxorubicin to tumors while sparing systemic exposure that drives the cardiotoxicity, myelosuppression, and other off-target effects that limit standard doxorubicin therapy. Chemically, faridoxorubicin is doxorubicin covalently bonded to the dipeptide N-(pyridine-4-carbonyl)-D-Ala-L-Pro (NCI Thesaurus C190682, FDA UNII 7XPB9B6MUA) — that dipeptide is the FAP-cleavable mask. The Phase 1a/1b trial ALS-6000-101 (NCT04969835) ran across salivary gland, urothelial, ovarian, breast and soft tissue sarcoma cohorts; it is listed as active but no longer recruiting, with actual primary completion on August 7, 2026.

What AVA6000 Is Investigated For

AVA6000 is Avacta's lead peptide-drug conjugate using its pre|CISION platform — FAP-activated tumor-selective delivery of doxorubicin. The mechanistic premise is elegant: doxorubicin is highly effective but limited by cardiotoxicity at lifetime cumulative doses; masking it with a FAP-cleavable peptide linker should produce tumor-selective release that reduces systemic exposure and the associated cardiotoxicity. The strongest evidence is preclinical: animal models demonstrated tumor-selective doxorubicin release and improved therapeutic index. Phase 1 ALS-6000-101 in FAP-expressing solid tumors began in 2022–2023, with preliminary clinical activity reported in conference proceedings through 2024–2026. The honest caveats: clinical Phase 1 data is preliminary and tumor-microenvironment-activated drug platforms have historically struggled with translation (the requirement for sufficient FAP expression, tumor accessibility, and adequate peptide-bond cleavage all need to align in human cancers as they do in animal models). The platform is more notable as proof-of-concept for FAP-targeted drug delivery than as a near-term approved cancer therapy.

History & Discovery

Salivary gland cancer as the anchor indication makes clinical sense: the disease is rare enough that Phase 2 basket-trial approaches such as DART SWOG S1609 (Chae et al., Ther Adv Med Oncol 2026, PMID 42499790) and HER2-targeted ado-trastuzumab emtansine (Ross et al., Clin Cancer Res 2026, PMID 42658187) are among the few peer-reviewed comparators in this disease at all. Neither is targeted therapy in the sense faridoxorubicin is — DART S1609 is dual checkpoint blockade and the Ross trial is a HER2-directed antibody-drug conjugate — but the response rates in those studies frame what a differentiated conjugate would need to beat. The ado-trastuzumab emtansine result is the uncomfortable one: a 58% response rate with 10.2-month median PFS in the salivary cohort is a higher bar than faridoxorubicin has so far cleared on response, though the two trials select patients on entirely different biomarkers. Avacta Therapeutics developed the pre|CISION platform around FAP-activated drug delivery as a tumor-microenvironment targeting strategy. AVA6000 was selected as the lead candidate using doxorubicin — a well-characterized and well-validated cytotoxic — as the payload, with the rationale that improving doxorubicin's therapeutic index through tumor-selective delivery would be valuable in multiple FAP-expressing cancer indications. The Phase 1a/1b trial (NCT04969835, org study ID ALS-6000-101) began on July 16, 2021 with multi-tumor enrollment across salivary gland, urothelial, ovarian, breast, and soft tissue sarcoma, and the first dose-escalation data was presented at AACR 2024 (abstract #CT188) and ESMO 2024 (abstract #646P). The International Nonproprietary Name 'faridoxorubicin' had been adopted in Avacta communications by the October 2025 ESMO press release; AVA6000 remains the development code, and the FDA records the substance under UNII 7XPB9B6MUA. The exact date of INN assignment is not recoverable from the published WHO INN lists. The clinical inflection point came on December 17, 2025 when Avacta announced the Phase 1b salivary gland cancer cohort readout: across 30 evaluable patients dosed ≥250 mg/m², the disease control rate reached 90% (2 confirmed partial responses, 7 minor responses with 10–<30% tumor shrinkage), median PFS was not reached at >15 weeks median follow-up, and 13 of 19 Phase 1b patients remained on therapy at the cutoff. That December release carried no cardiac-safety data; the cumulative-exposure and cardiac-toxicity findings often attributed to it actually come from the February 2026 protocol update and the ASCO 2026 presentation. It is worth being precise about what 550 mg/m² means, because it is routinely overstated. In Avacta's own trial it is a protocol-defined lifetime cap on released-doxorubicin exposure, not a pharmacological cliff. The best retrospective of conventional doxorubicin (Swain, Whaley and Ewer, Cancer 2003, PMID 12767102) estimated that 7% of patients developed doxorubicin-related congestive heart failure at a cumulative 550 mg/m² in earlier large-scale data, and 26% in their own pooled re-analysis of three trials — a serious rate, but not 'most patients'. The same paper is a caution against reading Avacta's LVEF numbers too confidently: more than half the patients who developed doxorubicin-related heart failure had a drop in ejection fraction of less than 30% while on study, and the authors concluded plainly that LVEF is not an accurate predictor of congestive heart failure in patients who receive doxorubicin. On February 3, 2026, Avacta announced two protocol updates: the historic maximum dosing limit, based on patient exposure to released free doxorubicin, was removed from the trial, and dose-level flexibility was added. That release reported the maximum cumulative exposure of released doxorubicin having been increased to 550 mg/m² during the trial with no severe cardiac toxicity observed. At ASCO 2026 on June 1, 2026 the programme reported four partial responses and nine minor responses among 38 evaluable patients, a disease control rate of 92% (35/38), and — across 111 patients dosed to that point — only four patients (<4%) with significant reductions in left ventricular ejection fraction and no cardiomyopathy events of any grade, with no meaningful relationship between LVEF change and released doxorubicin exposure even in the subset that reached the lifetime 550 mg/m² cap. At ESMO 2026 in Madrid on October 26, 2026 (poster 1549P, presented by Renata Ferrarotto and colleagues), Avacta reported median progression-free survival of 11.4 months (95% CI 7 months to not reached) in a 32-patient salivary gland cancer efficacy subset, against published historical benchmarks of 6–6.7 months, with three partial and six minor responses; 51 salivary gland patients had been enrolled across all doses and cohorts. This 32-patient subset is a different analysis set from the 38-patient ASCO cohort and the two should not be pooled. The registry tells a less buoyant story than the press releases. NCT04969835 is listed as ACTIVE_NOT_RECRUITING — closed to enrollment — with actual primary completion on August 7, 2026, estimated completion August 2027, and no results posted. No Phase 2 trial of faridoxorubicin has opened on ClinicalTrials.gov. Avacta's financing over the same period was hand-to-mouth for a company with two clinical assets: a fundraise of approximately £12.5m was proposed on October 5, 2026, the placing and subscription results followed on October 6, and trading in the shares was restored on AIM that same day, implying a prior suspension. The pre|CISION platform itself has expanded beyond faridoxorubicin: AVA6103 (FAP-exatecan) is the second clinical PDC, with first patient dosed March 31, 2026 in the FOCUS-01 Phase 1 (NCT07454642), and AVA6207 (a dual-payload PDC) was introduced at Avacta's 2026 Science Day. The FAP-activated drug delivery concept has been pursued by multiple companies with varying payloads and linker designs; faridoxorubicin represents one of the most advanced clinical programs in the space, with the doxorubicin payload providing a known clinical comparator for benchmarking the platform's therapeutic-index improvement.

How It Works

Doxorubicin is a powerful chemotherapy drug but has serious side effects, especially to the heart. AVA6000 is doxorubicin attached to a 'safety lock' (a peptide) that only opens up at tumor sites — where an enzyme called FAP (found mainly on cancer-supporting cells) cuts the peptide and releases the active drug. The goal is to keep the chemotherapy benefit while reducing the side effects to healthy tissues.

AVA6000 is a peptide-drug conjugate consisting of doxorubicin linked via a peptide bond to a sequence cleavable by fibroblast activation protein alpha (FAPα). FAPα is a serine protease in the dipeptidyl peptidase family with relatively restricted expression — high on cancer-associated fibroblasts (CAFs) in many solid tumors and on activated fibroblasts at sites of tissue remodeling and fibrosis, but minimal expression in healthy adult tissues. In circulation, AVA6000 is biologically inactive (the peptide masks doxorubicin's DNA-intercalating activity). At FAP-expressing tumor sites, FAPα cleaves the peptide bond releasing free doxorubicin in the tumor microenvironment, where it can be taken up by tumor cells and produce DNA damage through topoisomerase II inhibition and intercalation. The intended pharmacokinetic profile is high tumor-to-plasma doxorubicin ratio, reducing systemic exposure responsible for cardiotoxicity and other off-target effects. Key clinical questions include: (1) Does sufficient FAP activity exist in human tumors to produce therapeutic doxorubicin levels? (2) Does the reduced systemic exposure translate to clinically meaningful cardiotoxicity reduction? (3) Are FAP-expression-positive tumors a single responsive population, or is heterogeneity within that group? Phase 1 ALS-6000-101 is designed to address these in part.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about AVA6000:

• 01Zero peer-reviewed primary publications. PubMed returns no records for faridoxorubicin, AVA6000 or FAP-Dox. Every efficacy and safety figure on this page — the response rates, the 11.4-month PFS, the cardiac-safety claims — originates in company press releases and conference posters that have not been through peer review or published with full patient-level methods. This is the single most important caveat on the compound, and it has not changed in five years of clinical development.
• 02No Phase 2 trial has opened. The Phase 1a/1b closed to enrollment with actual primary completion in August 2026 and no results posted to ClinicalTrials.gov; Avacta has repeatedly described a transition to efficacy studies without registering one.
• 03Cardiotoxicity comparison versus standard doxorubicin — the key value proposition is reduced cardiotoxicity, requiring direct comparison in larger trials.
• 04FAP expression threshold for clinical response — patient selection biomarker development is ongoing.
• 05Tumor type selection — multiple FAP-expressing tumors are being evaluated; which respond best is being clarified.
• 06Combination strategies with immunotherapy or other agents.
• 07Whether the cardiac-safety advantage is real or an artifact of how it is measured. The programme's cardiac claim rests on LVEF, which the largest retrospective of conventional doxorubicin found is not an accurate predictor of heart failure — over half of patients who developed doxorubicin-related heart failure had an LVEF drop under 30%. Longer follow-up and a cardiac-biomarker endpoint would settle it; neither has been reported.

Forms & Administration

Intravenous infusion. Investigational. Not commercially available.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

AVA6000 is investigational and Phase 1 stage. Oncology management requires specialty care.

Timeline of Effects

Monitoring & Measurement

Common Questions

Who AVA6000 Is NOT For

Drug & Supplement Interactions

Doxorubicin-class drug interactions apply (cardiotoxic agents, certain CYP-inducing or -inhibiting medications, etc.). Specific AVA6000 drug interactions will be characterized in clinical development.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions