Technology
Products in Development
Xelcis Bio is progressing XELCIS XB through a comprehensive portfolio of oncology initiatives, spearheaded by TDOX, our XELCIS XB-doxorubicin conjugate. Three therapeutic programs are advancing to in vivo studies, while two additional programs focusing on protein delivery and nanobodies are expanding upon completed proof-of-concept research. Each program uses the same foundational platform, enabling insights from one to apply directly to subsequent projects.
Program Highlights
Each program is built on the same XELCIS XB core platform, with modality-specific conjugation chemistry tailored to the payload class.
TDOX — XELCIS XB-Doxorubicin
TDOX is our lead preclinical program: XELCIS XB surface-conjugated to doxorubicin via Z-Link self-immolative disulfide chemistry. It is designed to overcome multidrug resistance by improving intracellular doxorubicin concentration at the tumor site while reducing systemic and cardiac exposure.
Preclinical Data (3D Spheroid MDR Model)
9.5x greater cytotoxic potency vs. Doxil® (3D spheroid MDR model)
14x greater cellular uptake vs Doxil® (MDR cell line)
About 5x wider cardiomyocyte safety margin vs free doxorubicin (H9c2 in vitro)
Next milestone: in vivo study, with IND-enabling studies to follow. Lead expansion indication: platinum-resistant, recurrent ovarian cancer.
lead
XB-siBIRC5-DOX
A dual-payload program that co-conjugates doxorubicin with an siRNA silencing survivin (BIRC5), an apoptosis brake many tumors use to resist chemotherapy. Releasing the brake and delivering the cytotoxic to the same cell is designed to restore chemotherapy sensitivity in resistant tumors.
Status
Lead indication: advanced, anthracycline-naive undifferentiated pleomorphic sarcoma. In vivo studies planned. The construct is designed for ordered release, doxorubicin first, then the survivin silencer, matching the sequence-dependent biology.
In vivo Planned
XB-Protein / Peptide Therapeutics
XELCIS XB enables cytosolic delivery of protein therapeutics, an enduring challenge in drug delivery. In proof-of-concept studies, BSA and ovalbumin conjugates achieved efficient intracellular delivery and cytosolic release, demonstrating endosomal escape and validating XELCIS XB for functional delivery of intracellular proteins.
Proof-of-Concept Evidence
Proof-of-concept completed (BSA and ovalbumin). PCT conversion filed March 2026. Architecture parallels ADC and NDC delivery approaches. Open to partners.
POC Completed
XB-siPD-L1-DOX
A dual-payload chemo-immunotherapy program that co-conjugates doxorubicin with an siRNA silencing PD-L1, delivered together to the same tumor cell. Doxorubicin drives immunogenic tumor-cell death, while the siRNA lowers PD-L1, the checkpoint that tumors use to evade the immune system, addressing total PD-L1 rather than only the surface fraction that antibodies reach.
Status
Lead indication: PD-L1-positive triple-negative breast cancer. In vivo studies planned. Nucleic-acid and small-molecule co-conjugation disclosed in the XB-NT provisional filing.
In vivo Planned
XB-Nanobodies (Nanobody-Drug Conjugates)
XELCIS XB nanobody and nanobody-drug conjugates combine nanobody-based targeting with therapeutic payloads on the XELCIS XB nanoparticle, enabling controlled pharmacokinetics and cytosolic delivery. Independent conjugation preserves modularity, and the approach is engineered to overcome the size and endosomal-entrapment limits of conventional NDCs and ADCs.
De-Risking Evidence
Enabled by completed protein-delivery proof-of-concept (BSA and ovalbumin). Nanobody/NDC PCT conversion filed March 2026. Open to partners.
Seeking Partnership
XELCIS XB for Targeted Protein Degradation
PROTACs and molecular glues require cytosolic access to engage E3 ligases and drive targeted degradation. XELCIS XB extends to this class as a longer-horizon platform capability and a partnering opportunity.
IP Status
Provisional patent application for the XELCIS XB degradation platform has been filed. Open to partners.