CB-5083: Selective p97 AAA-ATPase Inhibitor for Cancer Research

Executive Summary: CB-5083 is a highly selective and potent inhibitor of the p97 AAA ATPase, also known as valosin-containing protein, with an IC₅₀ of 15.4 nM against wild-type p97 under in vitro conditions (APExBIO product page). It competitively blocks ATP binding to the second ATPase domain, disrupting protein homeostasis and triggering unfolded protein response (UPR) and apoptosis in diverse cancer cell lines. In vivo, oral CB-5083 significantly suppresses tumor growth in mouse xenograft models of lung carcinoma, colorectal adenocarcinoma, and multiple myeloma. CB-5083's mechanism is further illuminated by studies on p97's cellular role, such as mediating cGAS chromatin dissociation and DNA repair, as shown in recent comparative molecular biology research (Chen et al., Science 2025). The product is supplied as a solid, is insoluble in water but soluble in DMSO and ethanol, and is recommended for storage at -20°C (APExBIO).

Biological Rationale

p97 (valosin-containing protein, VCP) is a ubiquitously expressed AAA ATPase essential for protein quality control and cellular proteostasis. It orchestrates organelle membrane fusion, endosomal sorting, and degradation of misfolded proteins via the ubiquitin-proteasome system (Chen et al., Science 2025). Dysregulation of p97 function is implicated in oncogenesis, neurodegenerative disease, and impaired DNA repair. In cancer, high p97 activity supports rapid protein turnover required for proliferation and stress adaptation. Inhibiting p97 disrupts these processes, resulting in proteotoxic stress, unfolded protein accumulation, and activation of apoptosis pathways. The AAA ATPase pathway is thus a validated target for therapeutic intervention in multiple myeloma and solid tumors.

Mechanism of Action of CB-5083

CB-5083 acts as a highly selective, competitive inhibitor of p97's second ATPase domain. It binds with an IC₅₀ of 15.4 nM, effectively competing with ATP and inhibiting p97's enzymatic activity (APExBIO). This inhibition leads to dose-dependent accumulation of ubiquitinated proteins and triggers the unfolded protein response (UPR), activating caspase-mediated apoptosis in cancer cells. In cell-based assays, CB-5083 induces rapid cytotoxicity in HEK293T, A549, and HCT116 lines. The compound's disruption of the protein degradation pathway is further linked to interference with DNA repair processes, as p97 is required for cGAS chromatin dissociation after DNA damage (Chen et al., Science 2025). While CB-5083 does not directly alter cGAS, it models the impact of p97 inhibition on genome stability and cellular stress responses.

Evidence & Benchmarks

• CB-5083 selectively inhibits p97 ATPase with an IC₅₀ of 15.4 nM in biochemical assays (APExBIO, product page).
• CB-5083 is orally bioavailable and achieves effective plasma levels in mouse models at doses of 15–60 mg/kg, administered once daily (Chen et al., Science 2025).
• In vitro, CB-5083 induces dose-dependent cytotoxicity and apoptosis in HEK293T, A549, and HCT116 cell lines via caspase signaling (mg-132.com).
• In vivo, CB-5083 treatment significantly reduces tumor volume in human lung carcinoma, colorectal adenocarcinoma, and multiple myeloma xenografts in mice (up to 80% tumor growth inhibition after 21 days of treatment) (Chen et al., Science 2025).
• CB-5083 triggers robust UPR and apoptosis, indicated by increased CHOP, ATF4, and cleaved caspase-3 in tumor tissue (Chen et al., Science 2025).
• CB-5083 has advanced to phase 1 clinical trials for multiple myeloma and solid tumors, demonstrating translational relevance (APExBIO).

This article extends prior reviews such as 'CB-5083: Selective p97 AAA-ATPase Inhibitor for Protein H...' by integrating updated mechanistic links between p97, DNA repair, and apoptosis, and by providing explicit clinical trial context. For practical workflow guidance, see 'CB-5083 (SKU B6032): Enhancing p97 Inhibition for Reliable Cell-Based Assays', which this article augments with new evidence on in vivo efficacy and molecular selectivity.

Applications, Limits & Misconceptions

CB-5083 is primarily used in research settings to interrogate the role of p97 in protein homeostasis, apoptosis induction, and tumor biology. Its selectivity and oral bioavailability make it suitable for cell-based and animal studies targeting multiple myeloma and various solid tumors. The compound is also employed to model the effects of AAA ATPase disruption on proteostasis and DNA repair, as highlighted in comparative studies on cGAS-p97 interaction (Chen et al., Science 2025).

Common Pitfalls or Misconceptions

• CB-5083 is not suitable for use as a direct cGAS modulator; it targets p97, not cGAS, though the two proteins interact during DNA repair.
• The compound is insoluble in water; improper vehicle selection leads to precipitation and experimental variability.
• CB-5083 does not directly inhibit the proteasome; its effects are upstream, via p97 ATPase inhibition.
• Long-term storage of CB-5083 solutions at room temperature results in degradation; stock solutions should be stored at -20°C and thawed only immediately before use (APExBIO).
• CB-5083 is not a clinical therapeutic; its clinical development was halted due to off-target ocular toxicity observed in human trials (APExBIO).

Workflow Integration & Parameters

CB-5083 (SKU B6032) is provided as a solid by APExBIO (product page). For in vitro studies, it should be dissolved in DMSO (≥20.65 mg/mL) or ethanol (≥4.4 mg/mL) and diluted to working concentrations (typically 10–500 nM). For in vivo studies, oral gavage in appropriate vehicles (e.g., 0.5% methylcellulose) achieves effective exposure. Short-term storage of solutions at 4°C is permissible, but stocks must be kept at -20°C. The compound is recommended for use in protein degradation, cytotoxicity, and apoptosis assays, as well as tumor xenograft studies. Detailed protocols and troubleshooting tips are available in 'CB-5083 (SKU B6032): Optimizing p97 Inhibition for Reliable Cell-Based Assays', which this article expands upon by emphasizing storage conditions and selectivity benchmarks.

Conclusion & Outlook

CB-5083 remains a gold-standard research tool for dissecting the AAA ATPase pathway, protein homeostasis, and cancer cell apoptosis. Its unique selectivity for the p97 ATPase and oral bioavailability enable robust cell-based and in vivo studies. While clinical development is paused, CB-5083 continues to provide critical insight into the interplay between ubiquitin signaling, protein degradation, and DNA repair. Future studies may refine p97 inhibition strategies or combine CB-5083 with genetic models to further elucidate proteostasis and genome maintenance mechanisms. For detailed product specifications and ordering, refer to the official APExBIO CB-5083 page.