Fannin Partners has secured grant support from the Congressionally Directed Medical Research Programs and The Faris Foundation to advance a Raptamer-Drug Conjugate, or RapDC, programme targeting IL1RAP in Ewing sarcoma. Announced on August 14, 2026, the funding is intended to move an early-stage targeted therapeutic concept further through development rather than support a clinical trial, making the immediate milestone one of preclinical proof of concept rather than patient efficacy.
The distinction is important because the scientific rationale for IL1RAP is considerably more developed than the evidence supporting Fannin’s particular RapDC candidate. Published laboratory research has identified IL1RAP as a highly expressed cell-surface protein in Ewing sarcoma models and patient-derived material, while also linking the protein to mechanisms that may help tumor cells survive metastatic stress. Fannin is attempting to turn that biological vulnerability into a drug-delivery address, using a synthetic targeting molecule to carry a cytotoxic payload into IL1RAP-expressing cancer cells.
That creates an intriguing but still highly experimental proposition. RapDCs are designed around some of the same logic that has driven the growth of antibody-drug conjugates, namely separating the targeting component from the cell-killing payload and using a surface antigen to concentrate treatment in tumor cells. Fannin’s key departure is to replace the antibody with what it calls a Raptamer, a fully synthetic targeting molecule whose design is intended to allow programmable chemistry and site-specific payload conjugation.
Why does targeting IL1RAP provide a credible biological starting point in Ewing sarcoma?
The attraction of IL1RAP does not originate solely from Fannin’s programme. Research published in Cancer Research identified IL1RAP as strongly expressed in Ewing sarcoma and found that the protein contributed to cellular mechanisms associated with resistance to anoikis, a form of cell death triggered when cells detach from their normal environment. In experimental models, reducing IL1RAP activity impaired metastatic dissemination, while investigators also demonstrated that an IL1RAP-directed antibody could trigger antibody-dependent cellular cytotoxicity against Ewing sarcoma cells.
Those findings help explain why an internalizing IL1RAP surface target is potentially attractive for a drug-conjugate approach. A payload-delivery strategy generally requires more than simple antigen expression: the target must be sufficiently accessible and ideally internalize after the targeting molecule binds, allowing the conjugated drug to enter the malignant cell. Fannin says IL1RAP is expressed across the majority of Ewing sarcomas and is developing its RapDC programme around this internalization opportunity.
Interest in IL1RAP has also extended beyond antibody approaches. A 2026 preclinical study evaluated IL1RAP-directed CAR-modified natural killer cells in Ewing sarcoma models, adding further evidence that researchers consider the protein a potentially actionable cell-surface target. That work does not validate Fannin’s RapDC technology, but the emergence of multiple therapeutic strategies around the same antigen strengthens the argument that IL1RAP warrants continued investigation.
The remaining question is whether target biology translates into a therapeutic window. Expression within tumors must ultimately be considered alongside expression in normal tissues, payload potency, internalization efficiency, linker stability and systemic exposure. A surface antigen can be scientifically compelling without automatically becoming a successful drug target, particularly when a highly potent cytotoxic payload is attached.
How different are Fannin’s RapDCs from conventional antibody-drug conjugates?
Fannin describes RapDCs as conceptually similar to antibody-drug conjugates but built with synthetic Raptamers instead of antibodies. Its platform is designed to combine a targeting molecule with a cytotoxic payload and exploit an internalizing cell-surface receptor to deliver that payload into selected cancer cells.
The company has argued that synthetic targeting molecules could provide advantages including smaller molecular size, chemical manufacturing and more programmable conjugation. A 2024 American Association for Cancer Research abstract involving Fannin researchers discussed Raptamer-drug conjugates as potential molecularly targeted cancer therapeutics and positioned synthetic aptamer-like constructs as an alternative targeting modality to antibodies. Importantly, those assertions remain grounded in preclinical and conference-level development rather than comparative human evidence demonstrating that RapDCs outperform antibody-drug conjugates.
That gap will determine how the platform should currently be viewed. Antibody-drug conjugates have accumulated substantial clinical, manufacturing and regulatory experience across oncology, whereas Fannin’s RapDC platform remains at an earlier technological validation stage. Smaller and chemically synthesized targeting molecules may offer attractive engineering characteristics, but properties such as tumor penetration, pharmacokinetics, off-target uptake, payload release and therapeutic index will ultimately have to be demonstrated experimentally for individual candidates.
For Ewing sarcoma specifically, the programme therefore represents two simultaneous experiments. One is whether IL1RAP can function as a sufficiently selective drug-delivery target in the disease. The second is whether the Raptamer architecture can transport a cytotoxic payload with the exposure, stability and safety profile needed to justify progression toward human testing.
What do the CDMRP and Faris Foundation grants actually change for the programme?
The funding matters most because rare pediatric cancers can be difficult areas in which to finance very early development. Ewing sarcoma affects a relatively small patient population, and the commercial economics of preclinical drug discovery can make non-dilutive government and philanthropic support particularly valuable before a programme is mature enough for conventional venture or licensing investment.
The Congressionally Directed Medical Research Programs separately lists Fannin Partners, with Dev Chatterjee as principal investigator, among Fiscal Year 2025 Rare Cancers Research Program Concept Award applications recommended for funding. The Concept Award mechanism is specifically designed for innovative and untested concepts, anticipates proof-of-concept as its outcome and does not permit clinical trials. The programme allows total costs of up to $140,000 over as long as two years, although neither Fannin’s announcement nor the public award listing establishes that Fannin received the maximum amount.
There is also a procedural nuance. The CDMRP page published in July described Fannin’s application as recommended for funding and stated that federal funding remained contingent on negotiations and applicable policy. Fannin’s subsequent August 14 announcement described the support as a grant it had received, indicating that the company is presenting the funding as secured, but the exact financial terms were not disclosed in its announcement.
Fannin likewise did not disclose the size or detailed conditions of The Faris Foundation grant. The foundation has a history of supporting Ewing sarcoma and pediatric sarcoma research, including previous funding for research programmes involving recurrent and refractory sarcomas.
For the RapDC programme, the practical effect is therefore less about financing a direct leap into the clinic and more about funding experiments capable of answering whether the candidate deserves the next level of investment.
Why does relapsed and refractory Ewing sarcoma remain such a difficult development setting?
The clinical need provides the strongest reason to pursue unconventional therapeutic mechanisms. The National Cancer Institute describes recurrent Ewing sarcoma as having a poor prognosis and estimates five-year survival following recurrence at approximately 10% to 15%. It also notes that there is no standardized second-line treatment for relapsed or refractory disease, with chemotherapy, surgery, radiation and other investigational approaches used according to patient and disease characteristics.
Progress with targeted and immune-based treatments has been challenging. National Cancer Institute reviews describe limited activity from several previously investigated approaches in recurrent disease, including immune checkpoint inhibitors and some targeted therapies. That history is a useful caution against assuming that the identification of a biologically attractive target will automatically translate into durable clinical benefit.
At the same time, the limited therapeutic progress creates room for platforms that can attack the disease through different mechanisms. A targeted cytotoxic delivery strategy does not depend on the same biology as checkpoint blockade, nor does it necessarily require direct pharmacological inhibition of the EWSR1 fusion machinery that drives most Ewing sarcomas. If IL1RAP expression proves sufficiently consistent and accessible, it could potentially provide a practical surface marker through which a drug payload can be delivered.
That is still a series of conditional statements rather than a treatment claim. No clinical efficacy or safety evidence for Fannin’s Ewing sarcoma RapDC has been disclosed, and the company has not announced an Investigational New Drug application or human trial for this programme.
What milestones would move the IL1RAP RapDC programme beyond an interesting preclinical concept?
The most informative next results would demonstrate whether Fannin can reproduce selective IL1RAP binding across representative Ewing sarcoma models, quantify receptor internalization and show that payload delivery produces meaningful antitumor activity without unacceptable effects in normal tissue models. Pharmacokinetics, linker stability, biodistribution and dose-dependent toxicity will become increasingly important as the programme progresses from platform experiments toward a defined development candidate.
Candidate selection would represent another significant step because the term RapDC currently describes a therapeutic modality rather than a clinically characterized product. Investors, potential development partners and pediatric oncology researchers will eventually need details on the exact Raptamer construct, payload, linker chemistry, dosing strategy and tumor models supporting development.
Fannin already has a broader pediatric oncology footprint. Its announcement said the Ewing sarcoma project joins an osteosarcoma RapDC programme described as being in Investigational New Drug-enabling studies and Allterum Therapeutics’ CD127 antibody programme for acute lymphoblastic leukemia. Fannin’s own portfolio updates also show that the Allterum programme has previously advanced through Investigational New Drug clearance and into clinical development.
That broader pipeline could be strategically useful because experience gained in manufacturing, toxicology and regulatory interactions across one programme may inform another. It does not eliminate the need to validate each RapDC independently, particularly because changing the target, payload or molecular construct can materially alter pharmacology and safety.
For now, the grants move Fannin’s Ewing sarcoma programme forward without changing its evidence category. IL1RAP has a substantial preclinical rationale as a surface target, and independent research continues to investigate ways of exploiting it, but Fannin still has to demonstrate that its synthetic Raptamer architecture can convert that target biology into a reproducible therapeutic effect. The next meaningful inflection point will therefore not be another description of the platform’s theoretical advantages. It will be data showing that an IL1RAP-directed RapDC can selectively deliver its payload, control Ewing sarcoma models and establish a sufficiently credible safety margin to justify the far more demanding transition toward human development.