Fusion-Driven Targets Move to the Center of DSRCT Drug Development
Desmoplastic small round cell tumour (DSRCT) remains one of the most difficult solid tumors in pediatric and young-adult oncology. Survival beyond 5 years is still below 20%, and intensive multimodal care has not delivered a major long-term shift over the past three decades. The workshop convened by the sixth Paediatric Therapeutic Development Workshop series turned that frustration into a structured research agenda, ranking the most biologically credible targets and the drug formats most likely to reach patients.
At the heart of the discussion sits the defining oncogenic event: the EWSR1::WT1 fusion protein. In DSRCT, this fusion is not a passenger alteration but the central driver of malignant behavior, making it the most rational place to start when thinking about precision therapy. A therapy aimed directly at the fusion protein would, in theory, strike the disease where it is most dependent, rather than forcing treatment to rely only on cytotoxic chemotherapy and surgery.
The workshop also identified a more technically ambitious route: targeting a junction-derived neopeptide presented by HLA-A03 and HLA-A11 with a T-cell receptor approach. This strategy reflects a deeper level of tumor specificity, using the altered peptide generated by the fusion as an immune target. In practical terms, it is one of the few concepts in DSRCT that tries to exploit a molecular abnormality unique to the cancer itself, rather than a broadly expressed surface marker shared with healthy tissues.
Why Antibody-Drug Conjugates and TCR Therapy Rose to the Top
Several other targets were flagged as biologically interesting but still in need of stronger validation. These include LRRC15, SSTR3, SSTR5, NECTIN4, STEAP1 and mesothelin. Each has appeal because cell-surface or surface-adjacent antigens are often easier to drug than intracellular fusion proteins, yet the workshop stopped short of placing them among the most secure priorities. In a rare cancer with limited room for failure, preclinical plausibility alone is not enough; targets need to be consistent, tractable and relevant across the disease biology.
Among the modalities most likely to advance, antibody-drug conjugates directed at ERBB2/HER2 or claudin-6 were described as promising, and NTRK3 inhibition with a small molecule was also positioned as an active avenue. ADCs carry particular appeal in DSRCT because they can pair target recognition with potent intracellular cytotoxic payload delivery, potentially improving therapeutic selectivity in a disease that currently depends on broad, toxic regimens. A small molecule approach to NTRK3 offers a different path, especially if a meaningful dependence on that signaling axis can be confirmed in the right subset of tumors.
There is no targeted treatment approved for DSRCT, so the stakes around target choice are unusually high. A wrong bet costs years in a cancer that cannot afford them.
Existing Drugs Could Still Matter if Access Barriers Ease
Beyond new constructs, the workshop also ranked existing clinical assets for possible repositioning. The top priorities in this group were B7-H3, the DNA damage response, androgen signalling, FGFR4 and STEAP1. These candidates matter because they may allow DSRCT to move faster than waiting for a completely novel program to mature from first principles. Repurposing or redirecting agents already in development for other cancers can shorten the path to early-phase trials, provided the biology justifies the move.
The androgen axis deserves special attention because DSRCT occurs predominantly in post-pubertal males, and 80% of cases arise in that group. That epidemiology does not prove androgen dependence, but it does support closer study of sex hormone signaling in a disease with an unusual demographic skew. In a cancer this rare, even a modestly effective targeted strategy could have outsized value if it reduces the need for prolonged exposure to multi-agent chemotherapy.
The real barrier is not scientific imagination but trial access. Workshop participants identified obtaining therapeutics for clinical trials as a major obstacle, particularly when commercial incentives are weak and the patient population is tiny. For ultra-rare cancers, the distance between a good target and an enrolled patient can be longer than the distance between bench and bedside.
A Global Trial Structure Is Part of the Therapeutic Strategy
The rarity of DSRCT changes how drug development has to work. With slow accrual and scattered patients across continents, single-center efforts are unlikely to answer the most urgent questions efficiently. The workshop therefore called for a global initiative in preclinical and clinical research that would support international trials and collect patient data in a harmonized format.
That kind of infrastructure is not administrative overhead; it is part of the treatment plan. Standardized data capture would make it easier to compare outcomes across regions, define molecular subsets more consistently and identify whether a drug signal is real or simply a consequence of small numbers. It would also help preserve information from patients who receive off-label or compassionate-use therapy, which is often the only way rare-cancer evidence accumulates before formal trials can open.
Current management still relies on intensive multi-agent chemotherapy, cytoreductive surgery and whole-abdomen radiotherapy. These interventions can produce responses, but they are not curative for most patients, and acquired resistance is essentially universal after frontline treatment. The biological logic of the workshop’s recommendations is straightforward: if DSRCT is driven by a specific fusion and sustained by identifiable surface and signaling dependencies, then durable progress will require therapies built around those dependencies rather than repeated cycles of nonspecific cytotoxic pressure.
The Workshop’s Most Concrete Priority Is Coordination
The most actionable message from the workshop is not a single drug name but a development model. DSRCT needs both new agents and pragmatic testing of existing therapeutics, pursued in well-designed trials that can survive the logistical realities of an ultra-rare cancer. Without that dual approach, promising targets will remain isolated concepts, and patients will continue to rely on treatment combinations that have changed little in decades.
A second consequence follows from the biology itself. Because DSRCT is so dependent on a small number of central oncogenic and surface targets, the field may be able to move faster than its rarity suggests if collaborators align on which targets deserve immediate investment. The workshop offers that alignment, but the next step depends on whether drug developers, trial networks and international centers can convert a biologically coherent shortlist into studies that actually open for patients.