CB-5083: A Selective p97 Inhibitor for Tumor Growth Suppression

Executive Summary: CB-5083 is a selective, orally bioavailable inhibitor of p97 AAA ATPase, exhibiting a 15.4 nM IC50 against wild-type p97 in biochemical assays (APExBIO, product page). It disrupts protein homeostasis and triggers unfolded protein response (UPR) and apoptosis in multiple cancer cell lines. In xenograft mouse models, CB-5083 significantly inhibits tumor growth, demonstrating translational potential for multiple myeloma and solid tumor research (Y. Chen et al., 2025, DOI). The compound acts by competing with ATP at the second ATPase domain of p97 and is effective across cell types including HEK293T, A549, and HCT116. CB-5083 has advanced to phase 1 clinical trials, validating its relevance for drug discovery and mechanistic oncology studies.

Biological Rationale

The AAA ATPase p97, also known as valosin-containing protein (VCP), regulates protein homeostasis by facilitating organelle membrane fusion, endosomal cargo sorting, and protein degradation via the ubiquitin-proteasome system. Disruption of p97 function impedes proteostasis and is linked to cellular stress responses, unfolded protein response (UPR), and apoptosis. In the context of cancer, tumor cells rely on robust protein quality control to manage high rates of protein synthesis and misfolded protein burden. Targeting p97 disrupts this adaptive mechanism, sensitizing cells to endoplasmic reticulum (ER) stress and inducing cell death. Recent findings also implicate p97 in DNA repair, specifically in chromatin remodeling and the recruitment of DNA repair factors (Y. Chen et al., 2025, DOI). This expands the rationale for p97 inhibition in oncology and aging research.

Mechanism of Action of CB-5083

CB-5083 acts as a potent and selective inhibitor of the second ATPase domain (D2) of p97, competing with ATP binding. The compound's IC50 against wild-type p97 is 15.4 nM in biochemical assays. This specificity results in a dose-dependent blockade of p97-mediated protein unfolding and extraction from cellular complexes. Inhibition of p97 by CB-5083 leads to accumulation of polyubiquitinated proteins, triggering the unfolded protein response (UPR) and activating downstream apoptosis pathways, including caspase signaling. Notably, this mechanism is highly effective in cancer cells with elevated protein turnover and proteotoxic stress. Additionally, p97 inhibition may modulate DNA repair processes by altering the recruitment of homologous recombination (HR) factors such as FANCI and RAD50, further sensitizing tumor cells to genotoxic stress (Y. Chen et al., 2025).

Evidence & Benchmarks

• CB-5083 exhibits an IC50 of 15.4 nM against wild-type p97 in ATPase activity assays (APExBIO datasheet, product page).
• In vitro, CB-5083 induces dose-dependent cytosolic protein degradation and apoptosis in HEK293T, A549, and HCT116 cell lines (APExBIO datasheet, product page).
• Oral administration of CB-5083 in mouse xenograft models of lung carcinoma, colorectal adenocarcinoma, and multiple myeloma results in significant tumor growth inhibition and induction of UPR markers (Y. Chen et al., 2025, DOI).
• CB-5083 triggers caspase-dependent apoptosis, confirmed by increased cleaved PARP and caspase-3 in treated cancer xenografts (APExBIO, product page).
• CB-5083 has advanced to phase 1 clinical trials in multiple myeloma and solid tumor patients, supporting its translational relevance (APExBIO, product page).
• Mechanistic studies show that p97 inhibition by CB-5083 can interfere with DNA repair complex assembly, as p97 regulates cGAS retention and HR factor recruitment (Y. Chen et al., 2025, DOI).

For further mechanistic insights and translational context, see CB-5083: A Selective p97 Inhibitor Transforming Tumor Research, which provides foundational efficacy data. This article extends those findings by clarifying links to DNA repair and proteostasis in cancer models.

Applications, Limits & Misconceptions

CB-5083 is validated for use in studies of protein homeostasis disruption, cancer cell apoptosis induction, tumor growth inhibition in xenograft models, and unfolded protein response (UPR) pathway interrogation. It is a reference compound for p97 AAA ATPase signaling pathway research in oncology and DNA repair fields.

Common Pitfalls or Misconceptions

• CB-5083 is not broadly cytotoxic and requires specific concentrations to induce apoptosis; off-target effects at high concentrations are rare but possible in non-transformed cells.
• Its efficacy is cell-context dependent—non-cancerous cell lines may be less sensitive due to lower proteotoxic stress.
• CB-5083 does not directly inhibit DNA repair enzymes; its effect on HR is via p97 regulation of chromatin-associated factors, not by direct DNA interaction.
• CB-5083 is insoluble in water and requires DMSO or ethanol for dissolution; improper preparation can affect bioavailability and reproducibility.
• Long-term storage of prepared solutions (>1 week) at room temperature or above -20°C can lead to compound degradation and loss of potency.

For more on boundaries and practical deployment, see CB-5083 (SKU B6032): Empowering Reliable Protein Homeostasis Research—this guide addresses hands-on challenges not covered in the present mechanistic review.

Workflow Integration & Parameters

CB-5083 (SKU B6032) is supplied as a solid by APExBIO. It is insoluble in water but dissolves in DMSO (≥20.65 mg/mL) and ethanol (≥4.4 mg/mL). Recommended storage is at -20°C. For in vitro assays, working concentrations typically range from 10 nM to 2 μM, depending on cell line sensitivity and endpoint. For in vivo studies, oral gavage dosing in mouse xenografts should be determined based on tumor model and pharmacokinetic profiling. Avoid repeated freeze-thaw cycles and prepare fresh solutions when possible.

Researchers can integrate CB-5083 into established workflows for protein degradation, UPR pathway activation, and apoptosis readouts. Quantitative endpoints include measurement of polyubiquitinated proteins, UPR marker expression (e.g., CHOP, BiP), and apoptotic markers (e.g., cleaved caspase-3). For DNA repair studies, combine CB-5083 with DNA damage inducers to assess effects on HR versus non-homologous end-joining outcomes (Y. Chen et al., 2025).

This article updates the translational perspective found in CB-5083: A Selective p97 Inhibitor Transforming Cancer Research by providing new mechanistic evidence connecting p97 inhibition, UPR, and DNA repair in the context of tumor cell death.

Conclusion & Outlook

CB-5083 stands as a benchmark tool for dissecting the protein degradation pathway, selective p97 AAA-ATPase inhibition, and cancer therapeutics development. Its demonstration of efficacy in preclinical tumor models and advancement to clinical trials underscores its translational relevance for multiple myeloma and solid tumor research. Future studies should further delineate CB-5083’s impact on DNA repair processes and its potential for combination therapies targeting complementary stress response pathways. For more technical details and ordering information, visit APExBIO’s CB-5083 product page.