Cybrexa Therapeutics, a clinical-stage oncology biotechnology company based in New Haven, Connecticut, has unveiled promising new preclinical data for its tumor-targeting peptide-drug conjugate (PDC) technology at the ESMO Targeted Anticancer Therapies Congress 2025 in Paris, France.
The data, presented on March 4, 2025, demonstrates that the company's proprietary alphalex™ platform can selectively deliver potent microtubule inhibitors to tumor cells, effectively suppressing tumor growth while simultaneously inducing a durable anti-tumor immune response.
Novel pH-Driven Targeting Approach
Unlike conventional antibody-drug conjugates (ADCs) that target specific antigens, Cybrexa's alphalex™ PDCs employ a pH-driven targeting approach that exploits the acidic microenvironment characteristic of solid tumors. This antigen-agnostic mechanism potentially enables broader tumor applicability while avoiding toxicities commonly associated with antigen-based drug targeting.
"These data reinforce the potential of the alphalex platform to overcome the challenges of antigen-based therapies, while providing a powerful, tumor-selective approach to delivering cytotoxic agents," said Vishwas Paralkar, Ph.D., Chief Scientific Officer of Cybrexa Therapeutics. "In bypassing the limitations of antibody-drug conjugates, we are opening new therapeutic possibilities for patients with hard-to-treat solid tumors."
The alphalex™ technology platform consists of a pH-Low Insertion Peptide (pHLIP®), a linker, and a small molecule anticancer agent. The pHLIP peptides target acidic cell surfaces, enabling precise intracellular drug delivery that potentially reduces off-target effects while enhancing therapeutic impact.
Key Preclinical Findings
The poster presented at ESMO TAT 2025, titled "Characterization of Antigen-Agnostic Tumor-Selective Delivery and Immunomodulatory Activities of Auristatin and Maytansinoid alphalex™ Peptide-Drug Conjugates," highlighted several significant findings:
Tumor-selective drug delivery: Plasma stability and in vivo analyses confirmed that alphalex conjugates selectively deliver microtubule inhibitors to tumor tissue while sparing healthy immune cells.
Potent efficacy across multiple tumor models: As monotherapy, alphalex conjugates achieved complete tumor suppression in HCT116 human colorectal cancer models. In combination therapy scenarios using flank and metastatic models, the PDCs demonstrated synergy with doxorubicin and anti-PD-L1 therapy, further enhancing tumor suppression.
Durable anti-tumor immunity: The treatment induced immunogenic cell death that activated T- and B-cell responses, with evidence of tumor-binding IgG and long-term immune memory, supporting the potential for sustained anticancer effects.
Potential application after TOP1-based ADC treatment: The antigen-agnostic delivery of auristatin and maytansinoid payloads potentially positions alphalex PDCs as an option for patients who have progressed following topoisomerase-1 (TOP1)-based ADCs.
The preclinical studies evaluated the efficacy, safety, and immune-modulating effects of alphalex conjugates across multiple mouse and rat xenograft and syngeneic models, including colorectal, melanoma, renal, and breast cancers.
Clinical Development Progress
Cybrexa is actively advancing its alphalex platform in clinical trials. In October 2024, the company dosed the first patient in a Phase 2 clinical trial of CBX-12 for platinum-resistant or refractory ovarian cancer. CBX-12 is described as a first-in-class PDC that utilizes the alphalex technology to enhance intracellular delivery of exatecan, a potent topoisomerase-1 inhibitor.
This Phase 2 trial builds upon promising Phase 1 data that demonstrated broad activity across multiple tumor types, including ovarian, breast, non-small cell lung cancer, thymic, gallbladder, and colorectal cancers, alongside a manageable safety profile.
Potential Impact on Cancer Treatment Landscape
The alphalex platform's unique mechanism of action could represent a significant advancement in targeted cancer therapy. By targeting the acidic microenvironment common to solid tumors rather than specific antigens, Cybrexa's approach may overcome several limitations of current ADC therapies, including antigen heterogeneity and downregulation.
If successful in clinical development, this technology could potentially address unmet needs in treating various solid tumors, particularly for patients who have progressed on or are unsuitable for existing targeted therapies.
Founded in 2017, Cybrexa Therapeutics continues to develop its pipeline of PDC therapeutics with the goal of revolutionizing the standard of care in oncology. The company's technology originated from research conducted at Yale University and the University of Rhode Island, with pHLIP® exclusively licensed to pHLIP, Inc., of which Cybrexa is a sublicensee.
