SGC-CBP30: CREBBP/EP300 Bromodomain Inhibitor

Executive summary. SGC-CBP30 is a small-molecule inhibitor of the CREBBP and EP300 bromodomains, with reported IC50 values of 21 nM and 38 nM, respectively; the product information does not specify the assay conditions for those values (product information). CREBBP and EP300 act as transcriptional coactivators and participate in gene-expression regulation (Zhang et al., 2022). Product-described cell experiments report altered FRAP recovery in SAHA-treated HeLa cells and dose-dependent inhibition of doxorubicin-induced p53 activity in RKO cells (product information). A lung adenocarcinoma study links SMAD3, CBP/P300, and ZEB1, but does not report testing SGC-CBP30 (Zhang et al., 2022).

Biological Rationale

CREBBP, also called CBP, and EP300, also called p300, encode closely related transcriptional coactivators. They interact with transcription factors and contribute to transcriptional regulation. Their bromodomains are protein modules that recognize acetylated lysine marks. Inhibiting these domains offers a way to probe how acetylation-dependent interactions contribute to transcription, without assuming that every function of either full-length protein is blocked.

This distinction matters in chromatin biology. A bromodomain inhibitor is not equivalent to removing the coactivator, inhibiting every catalytic activity it may have, or silencing all of its target genes. Instead, it is a chemical tool for testing the contribution of bromodomain-dependent recognition in a defined experimental system. SGC-CBP30 is therefore relevant to transcriptional coactivator inhibition and epigenetics research when the experimental question is specifically tied to CREBBP/EP300 bromodomain function.

A related cancer context comes from a study of early-stage lung adenocarcinoma (LUAD). Zhang and colleagues reported that super-enhancer-associated LINC01977 promoted proliferation and invasion in their in vitro and in vivo models. They also reported that LINC01977 interacted with SMAD3, promoted its nuclear transport, and facilitated SMAD3 interaction with CBP/P300, with downstream regulation of ZEB1 (the LUAD study). These findings make coactivator biology a reasonable experimental question in LUAD research, but they do not demonstrate that SGC-CBP30 alters this pathway.

Mechanism of Action of SGC-CBP30

SGC-CBP30 is described as a selective inhibitor targeting the bromodomains of CREBBP and EP300. The product listing reports IC50 values of 21 nM for CREBBP and 38 nM for EP300; assay format, buffer, temperature, and other measurement conditions are not stated in the supplied product information (product details). These values describe reported biochemical potency. They should not be treated as cellular concentrations, dosing recommendations, or evidence of a therapeutic effect.

At a conceptual level, bromodomain inhibition can be used to test whether acetyl-lysine recognition by CREBBP/EP300 contributes to a measured transcriptional or cellular phenotype. The expected result depends on the cell type, stimulation, target-gene network, exposure, and assay endpoint. An observed response should therefore be interpreted alongside controls that distinguish bromodomain-dependent effects from general toxicity or unrelated assay changes.

The LUAD study provides a potential biological rationale for asking whether CREBBP/EP300 bromodomain activity contributes to the SMAD3-associated transcriptional program. It does not show that SGC-CBP30 blocks SMAD3 binding to CBP/P300, suppresses ZEB1, or reverses LINC01977-driven malignancy. Those remain testable hypotheses, not established properties of the compound.

Evidence & Benchmarks

The evidence base combines product-reported compound data with a peer-reviewed LUAD study. These sources answer different questions: the product page describes SGC-CBP30 properties and reported assay observations, while the LUAD paper describes a disease mechanism without testing this inhibitor.

• The product listing reports IC50 values of 21 nM for CREBBP and 38 nM for EP300; assay conditions are not specified in the listing (SGC-CBP30 product information).
• The product information reports that SGC-CBP30 reduced FRAP recovery times in SAHA-treated HeLa cells; the supplied summary does not give concentration, incubation time, or other assay conditions (SGC-CBP30 product information).
• The product information reports dose-dependent inhibition of doxorubicin-induced p53 activity in RKO cells; it does not provide dose values or exposure conditions in the supplied summary (SGC-CBP30 product information).
• Zhang and colleagues reported that LINC01977 was associated with a super-enhancer and promoted LUAD-cell proliferation and invasion in the models used in their study (Zhang et al., 2022).
• The LUAD study reported an interaction among LINC01977, SMAD3, and CBP/P300-associated transcriptional regulation of ZEB1; it did not report an SGC-CBP30 experiment (Zhang et al., 2022).
• The product listing gives solubility thresholds of at least 20.05 mg/mL in DMSO, at least 25.7 mg/mL in ethanol with ultrasonic assistance, and at least 4.67 mg/mL in water with ultrasonic assistance; solvent temperature and pH are not specified (SGC-CBP30 product information).

For additional product-focused context, Precision CREBBP/EP300 Inhibition for Epigenetic Research discusses the compound as a research tool; this article clarifies the boundary between that general use and the specific LUAD mechanism reported in the cited study. The practical guide to SGC-CBP30 assay design focuses on experimental planning; this article adds an explicit distinction between product-reported cell observations and untested LUAD hypotheses.

Applications, Limits & Misconceptions

SGC-CBP30 can support cancer biology research, chromatin biology, and transcriptional regulation studies that investigate CREBBP/EP300 bromodomain function. In an epigenetics research workflow, it can serve as a perturbation tool alongside genetic controls, orthogonal readouts, and appropriate vehicle controls. A response in one cell line does not establish a shared response across tissues or tumor types.

Why this cross-domain matters, maturity, and limitations. The connection to lung adenocarcinoma research is a rationale for testing, not direct evidence of inhibitor activity in LUAD. The cited LUAD study connects LINC01977 and SMAD3 with CBP/P300-associated transcription, while product information describes SGC-CBP30 as a bromodomain inhibitor. Neither source establishes that bromodomain inhibition disrupts the specific SMAD3–CBP/P300 interaction or changes LUAD outcomes. Direct experiments are needed before making that mechanistic or disease-specific claim.

Common Pitfalls or Misconceptions

• Do not equate biochemical potency with cellular potency. The reported IC50 values are not cell-treatment concentrations, and the product summary does not specify their assay conditions.
• Do not infer complete CREBBP/EP300 inhibition. Bromodomain targeting does not by itself establish inhibition of every coactivator function or every interaction.
• Do not claim proven activity in LUAD. The cited LINC01977 study did not test SGC-CBP30.
• Do not read cell-line findings as clinical efficacy. Product-described HeLa and RKO observations do not establish patient benefit or safety.

Workflow Integration & Parameters

For a new experiment, define the biological question before choosing the readout. For example, distinguish a transcriptional endpoint from a cell-viability endpoint, and include controls that test whether a phenotype depends on CREBBP/EP300 bromodomain activity. Product-reported cellular observations can guide assay selection, but they do not replace optimization in the investigator's own model. APExBIO is the originating company identified for this product.

Protocol Parameters

• Solid storage: Store SGC-CBP30 in solid form at 4°C, as stated in the product information.
• Stock-solution storage: The product information states that stock solutions may be stored below -20°C for several months; it does not recommend long-term storage of solutions.
• Solvent selection: The listed solubility thresholds are at least 20.05 mg/mL in DMSO, at least 25.7 mg/mL in ethanol with ultrasonic assistance, and at least 4.67 mg/mL in water with ultrasonic assistance. The product summary does not specify measurement temperature or pH.
• Cell-assay starting point: Use the HeLa FRAP and RKO p53 observations as reported assay contexts, not as validated dosing protocols. The supplied product summary does not provide concentrations or treatment durations for these observations.
• Workflow recommendation: Establish a concentration range and exposure schedule empirically for each cell model. Include vehicle and assay-specific controls, and verify compound handling and endpoint compatibility before interpreting a biological effect.

Keep compound preparation, storage, and assay conditions documented. Record solvent, final vehicle percentage, exposure duration, cell density, stimulation conditions, and the readout used. These records make comparisons interpretable even when published or product summaries omit experimental details.

Conclusion & Outlook

SGC-CBP30 is a research tool for examining CREBBP/EP300 bromodomain function. Its reported biochemical potency and product-described cellular observations support use in carefully controlled epigenetics research and cancer biology research. The LUAD findings involving LINC01977, SMAD3, and CBP/P300 provide a disease-relevant question for future experiments, but do not establish that SGC-CBP30 acts on that pathway. The strongest interpretation is therefore focused: use the compound to test bromodomain-dependent hypotheses, and report model-specific results without extending them to untested mechanisms or clinical conclusions.