Avacta Therapeutics (LSE: AVCT) has received Investigational New Drug (IND) clearance from the United States Food and Drug Administration for AVA6103 (also known as FAP-Exd), its second clinical-stage asset developed using the company’s proprietary pre|CISION platform. The IND clearance enables the start of a Phase 1 trial evaluating the safety, tolerability, and dose parameters of AVA6103 in adults with solid tumors, including pancreatic, cervical, gastric, and small cell lung cancers. The study is expected to begin enrollment in the first quarter of 2026.

AVA6103 is a peptide drug conjugate (PDC) that links the highly potent topoisomerase I inhibitor exatecan to a tumor-activated substrate targeting fibroblast activation protein (FAP), a protease overexpressed in many solid tumors. Unlike antibody-drug conjugates that require cell surface receptor binding and internalization, Avacta’s approach relies on extracellular cleavage by tumor-localized proteases, releasing the drug payload directly into the tumor microenvironment. The result is a protease-specific sustained release mechanism that could, if proven in human trials, enable a more favorable therapeutic index for exatecan—a drug historically hampered by systemic toxicity.

AVA6103 represents a key inflection point in the pursuit of site-activated cytotoxic delivery

The clearance of AVA6103 is significant not only because it marks the second clinical program from Avacta Therapeutics but also because it tests whether protease-based activation can meaningfully unlock the clinical value of cytotoxic agents deemed too risky for systemic administration. Exatecan is far more potent than irinotecan, another topoisomerase I inhibitor, but prior clinical attempts to deploy exatecan have been stymied by narrow safety margins. What Avacta is proposing with AVA6103 is a chemistry-first strategy that bypasses systemic circulation via FAP-triggered release, potentially restoring clinical utility to a drug that failed not for lack of efficacy but due to toxic exposure outside tumors.

Industry observers believe AVA6103 may test the real-world feasibility of site-activated PDCs in a way antibody-based constructs cannot. The compact size of peptides compared to antibodies could offer better tumor penetration, faster clearance of inactive conjugates, and reduced off-target effects. This is particularly important for exatecan, where controlling systemic exposure is paramount.

Dual-arm dosing strategy signals uncertainty around optimal exposure and release kinetics

Avacta Therapeutics has designed the AVA6103 trial with two parallel arms: one administering the drug every two weeks (Q2W) and the other every three weeks (Q3W). The dual-dosing approach reflects uncertainty about the in-human pharmacokinetics of the platform’s sustained release profile. While preclinical models may have offered a theoretical foundation for dose scheduling, the real-world activation rate of the FAP-cleavable linker in diverse human tumors remains unproven.

This design nuance points to a broader limitation with novel delivery platforms. Until pharmacodynamics are better understood in the context of patient variability, including the degree and pattern of FAP expression in tumors, dose intensity and duration remain critical unknowns. This also raises the stakes for the initial dose escalation cohort, where safety and tolerability data will directly influence the clinical development trajectory of not just AVA6103 but the entire pre|CISION pipeline.

AI-informed tumor selection adds a precision oncology layer to the delivery strategy

In a bid to sharpen its patient selection framework, Avacta Therapeutics partnered with Tempus AI to identify tumor types that express FAP and demonstrate intrinsic sensitivity to topoisomerase I inhibition. This led to the prioritization of pancreatic, cervical, gastric, and small cell lung cancers for the AVA6103 trial. The use of AI to match microenvironmental biomarkers with drug susceptibility reflects a growing trend in oncology trial design, especially for platforms that depend on local activation rather than systemic pharmacology.

The integration of FAP expression with drug sensitivity algorithms could theoretically increase the odds of early clinical efficacy, particularly in dose-finding cohorts where sample sizes are small. However, success here will depend on the reproducibility of FAP expression across tumor subtypes and stages. If expression proves patchy or context-dependent, then the tumor specificity premise behind the entire pre|CISION approach may require reevaluation.

How AVA6103 differs from exatecan-based ADCs already in development

Several oncology companies, including Daiichi Sankyo and AstraZeneca, have developed or licensed antibody-drug conjugates based on exatecan derivatives. These ADCs use monoclonal antibodies to target cell surface antigens like HER2 or TROP2, delivering the payload upon internalization. While clinically effective, these ADCs face challenges including low antigen expression in some tumors, limited penetration in large or fibrotic tumors, and off-target effects in normal tissues that express the same antigens at lower levels.

AVA6103 takes a different route. It bypasses surface receptor targeting and instead leverages a tumor-expressed enzyme to trigger release of its payload. This extracellular cleavage strategy, enabled by a proprietary peptide linker that is selectively cleaved by FAP, offers two theoretical advantages: deeper tissue penetration due to the small size of the PDC and reduced off-target toxicity due to limited systemic exposure. Whether these benefits can be realized in humans remains to be seen, but the approach carves out a distinct niche in the exatecan development landscape.

Platform-level validation will hinge on more than just safety and efficacy signals

For Avacta Therapeutics, the AVA6103 study is about more than demonstrating tolerability or tumor shrinkage. It is a platform-level readout. The pre|CISION chemistry, which centers on tumor-specific protease activation, must now prove that it can consistently trigger payload release under physiological conditions without introducing off-target cleavage, metabolic instability, or manufacturing complications.

This is especially important given that the first pre|CISION asset, AVA6000 (a doxorubicin conjugate), has already generated promising safety data. AVA6103 introduces a more potent payload in exatecan, which raises the bar for linker stability and tumor specificity. If systemic toxicities appear even at low doses, the platform’s foundational claim of reduced systemic exposure could be undermined. On the other hand, if AVA6103 demonstrates clean delivery with measurable anti-tumor activity, it could open the door to additional payloads and potentially accelerate regulatory engagement.

Manufacturing scalability and linker control remain unresolved development challenges

While Avacta Therapeutics has emphasized the speed of AVA6103’s IND preparation—completed within 24 months—questions remain around manufacturing scale-up, linker consistency, and regulatory standardization. Peptide-drug conjugates, though simpler than antibody-drug conjugates in some respects, still face formulation and stability challenges. The proprietary nature of the linker and capping chemistry also introduces potential bottlenecks in terms of batch reproducibility, purification, and long-term storage.

If AVA6103 advances beyond Phase 1, scalability will become an increasingly central issue, especially if future combinations with immunotherapy or radiotherapy are explored. For now, the small patient cohorts in dose escalation may mask these risks, but platform adoption by larger biopharma partners or investors will likely require demonstration of both clinical feasibility and supply chain resilience.

What stakeholders across the oncology ecosystem are watching for in 2026

Clinicians, regulators, and investors will be looking closely at early data expected in the second half of 2026. For clinicians, the key question is whether AVA6103 can deliver exatecan-like potency without incurring the hematological or gastrointestinal toxicities that derailed its predecessors. Regulators will focus on the strength of the dose-response signal and the clarity of the pharmacokinetic and pharmacodynamic data. Investors, meanwhile, will be assessing whether the platform can scale, whether the biomarker strategy translates into predictable efficacy, and whether differentiation from ADCs is compelling enough to support value creation.

Importantly, any indication that FAP expression correlates poorly with tumor response could weaken the platform’s mechanistic narrative. Likewise, if AVA6103’s clinical activity is indistinguishable from prior exatecan constructs, enthusiasm for a protease-triggered approach may wane. But if early readouts show tumor-specific activation, manageable toxicity, and signs of anti-tumor efficacy, Avacta Therapeutics may be positioned to push beyond traditional delivery modalities and expand the use of highly potent cytotoxics in oncology.

  AVA6103, Avacta Therapeutics, exatecan, FAP-Exd, FDA IND, peptide drug conjugates, Phase 1 trials, pre|CISION, solid tumors, topoisomerase I inhibitors