Avacta Therapeutics has opened the Phase 1 clinical trial of FAP-Exd (AVA6103), its second pipeline candidate and the first sustained-release peptide drug conjugate built on the company’s tumor-activated pre|CISION platform. The trial, which opened enrollment at two U.S. specialty oncology sites in Virginia and Texas in mid-March 2026, will test the agent in patients with advanced pancreatic cancer, cervical and vulvar cancer, gastric and gastroesophageal junction cancers, and small cell lung cancer. The IND clearance was granted by the FDA in January 2026, and the company expects the first patient to enroll before the end of March.
Why the payload history matters more than the platform narrative
To understand what Avacta is attempting with FAP-Exd, the prior clinical biography of exatecan is essential context. The compound, a water-soluble hexacyclic camptothecin analogue, was evaluated extensively as a single agent in the late 1990s and early 2000s. Phase I studies established that its dose-limiting toxicities were predominantly haematological, including neutropenia and thrombocytopenia, and development as a standalone therapy was ultimately discontinued. Exatecan never reached commercial approval as a conventional drug. The reason it is attracting renewed clinical attention today is that its potency as a topoisomerase I inhibitor, roughly three to ten times greater than that of topotecan and SN-38 respectively, was never in doubt. The problem was systemic exposure, not cytotoxic efficacy.
The broader revival of exatecan has been driven primarily by the antibody-drug conjugate field. Deruxtecan, a close structural derivative, is the payload in trastuzumab deruxtecan, the AstraZeneca and Daiichi Sankyo product that achieved major regulatory approvals in HER2-positive breast cancer and gastric cancer. That commercial success established that exatecan derivatives can be managed within a targeted delivery framework. Avacta is now attempting a conceptually distinct route: using a small peptide cleaved by fibroblast activation protein, or FAP, rather than a large antibody, to deliver the payload directly to the tumor stroma. The pre|CISION mechanism bypasses the manufacturing and pharmacokinetic constraints of monoclonal antibody conjugates, but it also means Avacta enters the clinic without the established antibody anchor that has underpinned the ADC wave.
What the sustained-release mechanism is designed to solve
The distinguishing feature of AVA6103 relative to both earlier exatecan formulations and current ADC approaches is the sustained-release kinetic profile Avacta has engineered into its FAP-cleavable peptide chemistry. Preclinical data presented at the American Association for Cancer Research annual meeting in April 2025 and supplemented by pharmacology data released in December 2025 showed that a single dose of FAP-Exd can generate active exatecan concentrations in the tumor over a period exceeding 60 hours, compared with the approximately nine-hour half-life of conventional exatecan in circulation. The company’s own comparative analysis, published in early 2026 and using an AI-reconstructed synthetic dataset from a published AstraZeneca study, suggested that FAP-Exd achieves a higher maximum drug concentration in tumor tissue than trastuzumab deruxtecan, and does so more rapidly. The tumor selectivity index, measuring tumor exposure versus systemic exposure over 14 days, was reported to favour the pre|CISION approach.
Clinicians and pharmacologists tracking the field will note that these comparisons rely on animal model data and an AI-constructed synthetic arm rather than direct head-to-head clinical pharmacokinetics. The conversion of preclinical pharmacokinetic advantages into human benefit is the precisely the question the Phase 1 trial must begin to answer. The Q2W and Q3W parallel dosing arms in the Phase 1a escalation design will generate early data on the human pharmacokinetic profile, and the simultaneous collection of both tumor and plasma pharmacokinetics is a notable feature that will allow direct calculation of tumor selectivity indices in human tissue for the first time.
Indication selection and the role of FAP co-expression data
The four tumor types selected for the Phase 1 cohort reflect a deliberate strategy rather than opportunistic selection. Avacta has referenced a collaboration with Tempus AI to apply large-scale genomic and expression databases to the question of which cancers are most likely to respond based on co-expression of FAP and SLFN11, a DNA repair factor associated with response to topoisomerase I inhibition. Pancreatic cancer, small cell lung cancer, and gastric cancer are all characterised by high FAP expression at the tumor-stroma interface and, historically, by limited responses to conventional systemic chemotherapy. Cervical and vulvar cancers were also identified through this AI-assisted selection process.
The AI-driven indication selection is analytically interesting but also raises a verification question that the trial will need to address. SLFN11 expression is a biomarker of predictive utility across multiple tumor types, but its measurement in clinical biopsy specimens is not yet standardized, and the threshold for meaningful co-expression with FAP has not been prospectively validated in a clinical cohort. Whether the trial will require or collect SLFN11 status as part of its stratification or biomarker protocol has not been disclosed in current public materials. Industry observers will be watching whether Avacta embeds prospective biomarker collection into the Phase 1 design, which would materially strengthen the analytical value of the eventual dataset.
Trial design strengths and the open questions remaining
The Phase 1a dose-escalation design follows conventional oncology Phase 1 methodology: a dose-finding study with parallel schedule arms in a heavily pretreated advanced cancer population. The enrollment of patients across four distinct tumor types in a single escalation cohort is efficient from a regulatory and timeline standpoint but introduces heterogeneity that can complicate pharmacodynamic interpretation in a small early-phase dataset. Preliminary safety and pharmacokinetic data are expected in the second half of 2026, which is consistent with the anticipated enrollment pace if the first patient enters before the end of March.
The speed of development from concept to IND clearance, achieved by Avacta in approximately 24 months by the company’s own account, is notable for a small AIM-listed clinical-stage biotech operating without a major pharma partner on this program. Whether that pace reflects genuinely accelerated development or a degree of compressed preclinical de-risking will only become clear when the Phase 1 human safety data emerge. The sustained-release mechanism is the principal differentiating claim, and its tolerability profile relative to conventional exatecan is the primary clinical question. Preclinical data showed high tumor selectivity and prolonged complete responses in patient-derived xenograft models, including models resistant to topoisomerase I inhibition. Translating that finding to patients with advanced disease who are likely to have received multiple prior lines of therapy, including potentially irinotecan or other camptothecin derivatives, represents the core clinical challenge ahead.
Competitive positioning in the exatecan and PDC landscape
Avacta is not the only company attempting to rehabilitate exatecan’s clinical profile through targeted delivery. CBX-12, a pH-sensitive peptide-exatecan conjugate from Cybrexa Therapeutics, has been investigated in clinical trials. Anti-CEACAM5 ADCs carrying exatecan payloads have entered Phase 1 trials in colorectal cancer, with early clinical data showing activity in heavily pretreated patients. Multiple additional exatecan ADCs are in clinical development across breast, lung, and gastrointestinal cancer indications. The broader competitive landscape for tumor-targeted topoisomerase I inhibitors is therefore crowded and well-resourced, with AstraZeneca and Daiichi Sankyo holding a substantial commercial head start with their approved deruxtecan franchise.
Where Avacta’s pre|CISION platform could differentiate is in its target biology. FAP is a stromal protease that is consistently overexpressed across a broad range of solid tumors but is largely absent in normal adult tissue, making it a logically attractive activation switch for a highly potent payload. Unlike HER2 or Trop2, which require specific antigen expression on the tumor cell surface, FAP-driven activation depends on the stromal microenvironment rather than individual tumor cell phenotype. This could, in principle, allow AVA6103 to reach patients whose tumors have lost or never expressed conventional ADC targets. Whether that theoretical breadth translates into actual clinical activity across a diverse patient population remains the central unanswered question as the trial begins enrollment.
What clinicians and regulators will be watching in the second half of 2026
The preliminary safety and pharmacokinetic data expected in the second half of 2026 will be the first human evidence for whether the pre|CISION sustained-release mechanism performs as the preclinical data suggest. Regulatory observers will be particularly focused on whether haematological toxicities, the dose-limiting constraint that ended conventional exatecan development, are mitigated at pharmacologically relevant doses. Signs of early tumor response in the preliminary efficacy data, while not the primary objective of the Phase 1a portion, would be significant given the heavily pretreated nature of the enrolled population and the historically difficult-to-treat indications selected. Avacta’s first clinical program, FAP-Dox (AVA6000), a pre|CISION doxorubicin conjugate, has demonstrated activity in salivary gland cancers in its Phase 1b expansion cohorts, which gives the platform a degree of human proof-of-concept, though the payloads and mechanisms differ.
The parallel investigation of two dosing schedules in Phase 1a is a practical design choice that allows the company to gather comparative pharmacokinetic and tolerability data without running a second standalone trial. Which schedule best supports the sustained-release pharmacology of AVA6103 is currently unknown, and the answer will shape the Phase 1b expansion design and any subsequent regulatory submission strategy. For a program that has moved from concept to first patient in two years, the next six months represent the transition from platform promise to human evidence.
Avacta’s pre|CISION exatecan conjugate reaches Phase 1 as competition in targeted topo I inhibitors intensifies added by Pallavi Madhiraju on
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