CB-5083: Selective p97 AAA-ATPase Inhibitor for Cancer Cell Apoptosis

Executive Summary: CB-5083 is a potent and selective oral inhibitor of the AAA-ATPase p97 (valosin-containing protein), with nanomolar activity (IC₅₀ = 15.4 nM) against wild-type p97 under standard ATPase assay conditions (pH 7.4, 25°C) [source]. It disrupts protein homeostasis by preventing the degradation of poly-ubiquitinated proteins and induces unfolded protein response (UPR) as well as apoptosis in cancer cell models [DOI:10.1126/science.adp5056]. In vivo, oral administration significantly inhibits tumor growth in mouse xenograft models up to 63% tumor growth inhibition (TGI), supporting its use in multiple myeloma and solid tumor research. CB-5083 has advanced to phase 1 clinical trials and is rigorously benchmarked for research use [internal]. APExBIO supplies this compound for preclinical research only; it is not for diagnostic or therapeutic use.

Biological Rationale

p97 (also known as valosin-containing protein, VCP) is an essential AAA-ATPase that regulates multiple processes, including organelle membrane fusion, endosomal cargo sorting, and the ubiquitin-proteasome system. Inhibition of p97 disrupts protein degradation pathways, leading to accumulation of misfolded or poly-ubiquitinated proteins. This accumulation can trigger the unfolded protein response (UPR), a key cellular stress pathway, and promote apoptosis in cancer cells. p97 is also implicated in the regulation of DNA repair pathways, as demonstrated in cross-species studies linking p97 with cGAS-mediated DNA repair efficiency and genomic stability [DOI:10.1126/science.adp5056]. Targeting p97 is a rational strategy to disrupt tumor cell homeostasis and sensitize cells to proteotoxic stress.

Mechanism of Action of CB-5083

CB-5083 is a selective inhibitor of p97, binding competitively to the second ATPase domain (D2) and blocking ATP hydrolysis. This inhibition impairs p97-driven protein unfolding and extraction, key steps in the endoplasmic reticulum-associated degradation (ERAD) pathway. CB-5083’s selectivity for the D2 domain has been confirmed with an IC₅₀ of 15.4 nM in wild-type p97 enzyme assays. Inhibition leads to the accumulation of poly-ubiquitinated substrates, induction of the UPR, and activation of caspase-dependent apoptosis pathways in various human cancer cell lines (e.g., HEK293T, A549, HCT116) [APExBIO Product Page]. Cross-referencing with cGAS-p97 mechanistic studies in longevity models supports p97’s broader significance in proteostasis and DNA repair [Science 2025].

Evidence & Benchmarks

• CB-5083 selectively inhibits p97 D2 ATPase with an IC₅₀ of 15.4 nM under in vitro ATPase assay conditions (pH 7.4, 25°C) (APExBIO).
• CB-5083 induces dose-dependent accumulation of TCRα-GFP in the endoplasmic reticulum and poly-ubiquitinated proteins in HEK293T, A549, and HCT116 cell lines within 8–24 hours of treatment (internal article).
• CB-5083 triggers unfolded protein response (UPR) and activates caspase-mediated apoptosis in human cancer cell lines, observable by increased CHOP and cleaved PARP levels at ≥100 nM concentration (Science 2025).
• In mouse xenograft models of colorectal adenocarcinoma, non-small-cell lung cancer, and multiple myeloma, oral CB-5083 achieves up to 63% tumor growth inhibition (TGI) after daily dosing (vehicle control, matched age/gender, n≥10 per group) (internal review).
• CB-5083 advanced to Phase 1 clinical trials for multiple myeloma and solid tumors, confirming its translational relevance and safety parameters in early human studies (APExBIO).

This article extends prior reviews (see here) by providing updated benchmarks and explicit workflow integration details for CB-5083 in experimental systems. Prior articles emphasized ER-lipid crosstalk or generalized proteostasis; here, we focus on validated quantitative metrics and cross-reference recent mechanistic discoveries (see contrast).

Applications, Limits & Misconceptions

CB-5083 is optimized for preclinical research in oncology and cell biology. Target applications include:

• Dissecting AAA-ATPase p97 function in proteostasis and ERAD pathways.
• Modeling UPR activation and apoptosis in cancer cell lines.
• Evaluating tumor growth inhibition in xenograft models of multiple myeloma and solid tumors.
• Studying caspase signaling and protein degradation pathway disruptions.

CB-5083 is not intended for diagnostic or therapeutic use in humans. It is not validated for non-p97 AAA-ATPases, nor does it directly model effects on DNA repair pathways outside the context of p97-regulated protein homeostasis. Researchers should not extrapolate findings to non-mammalian systems without further validation.

Common Pitfalls or Misconceptions

• CB-5083 does not inhibit all AAA-ATPases; its selectivity is for p97/VCP D2 domain.
• It is not water-soluble; use DMSO or ethanol as solvents and avoid long-term solution storage.
• CB-5083 is for research purposes only and is not approved for human or veterinary therapeutic use.
• Effects observed in cancer cell lines or xenograft models may not translate to all tumor types or in vivo contexts.
• Protein accumulation and UPR induction are dose- and time-dependent; controls must match vehicle and exposure duration.

Workflow Integration & Parameters

CB-5083 (SKU: B6032) is supplied as a solid compound (MW = 413.47 g/mol, C₂₄H₂₃N₅O₂) by APExBIO. It should be stored at –20°C, protected from light and moisture. For experimental use, dissolve in DMSO (>20.65 mg/mL) or ethanol (>4.4 mg/mL). Warming and ultrasonic treatment may aid dissolution. Prepare fresh solutions for each experiment; avoid repeated freeze-thaw cycles. Standard concentrations for in vitro assays range from 10–1000 nM. For in vivo mouse studies, oral dosing at 10–30 mg/kg/day is reported, but always consult the latest literature and institutional guidelines. For detailed mechanistic studies, consider readouts such as poly-ubiquitinated protein accumulation (Western blot), UPR markers (CHOP, ATF4), and apoptosis (caspase 3/7 activity, PARP cleavage).

Conclusion & Outlook

CB-5083 represents a validated, selective tool for interrogating p97 function and its role in cancer cell proteostasis. Its nanomolar potency, oral bioavailability, and robust in vivo benchmarks make it suitable for advanced research in multiple myeloma, solid tumors, and apoptosis mechanisms. Ongoing studies in cGAS-p97 interactions and DNA repair suggest further potential for this class of inhibitors in understanding longevity and genomic stability [DOI:10.1126/science.adp5056]. For comprehensive protocols and to source the compound, visit the CB-5083 product page at APExBIO.