The ABCB1 and ABCG2 efflux transporters limit brain disposition of the SYK inhibitors entospletinib and lanraplenib.

The highly selective Spleen Tyrosine Kinase (SYK) inhibitors entospletinib and lanraplenib disrupt kinase activity and inhibit immune cell functions. They are developed for treatment of B-cell malignancies and autoimmunity diseases. The impact of P-gp/ABCB1 and BCRP/ABCG2 efflux transporters, OATP1a/1b uptake transporters and CYP3A drug-metabolizing enzymes on the oral pharmacokinetics of these drugs was assessed using mouse models. Entospletinib and lanraplenib were orally administered simultaneously at moderate dosages (10 mg/kg each) to female mice to assess the possibility of examining two structurally and mechanistically similar drugs at the same time, while reducing the number of experimental animals and sample-processing workload. The plasma pharmacokinetics of both drugs were not substantially restricted by Abcb1 or Abcg2. The brain-to-plasma ratios of entospletinib in Abcb1a/b-/-, Abcg2-/- and Abcb1a/b;Abcg2-/- mice were 1.7-, 1.8- and 2.9-fold higher, respectively, compared to those in wild-type mice. For lanraplenib these brain-to-plasma ratios were 3.0-, 1.3- and 10.4-fold higher, respectively. This transporter-mediated restriction of brain penetration for both drugs could be almost fully inhibited by coadministration of the dual ABCB1/ABCG2 inhibitor elacridar, without signs of acute toxicity. Oatp1a/b and human CYP3A4 did not seem to affect the pharmacokinetics of entospletinib and lanraplenib, but mouse Cyp3a may limit lanraplenib plasma exposure. Unexpectedly, entospletinib and lanraplenib increased each other's plasma exposure by 2.6- to 2.9-fold, indicating a significant drug-drug interaction. This interaction was, however, unlikely to be mediated through any of the studied transporters or CYP3A. The obtained insights may perhaps help to further improve the safety and efficacy of entospletinib and lanraplenib.

ABCB1 limits brain exposure of the KRASG12C inhibitor sotorasib, whereas ABCB1, CYP3A, and possibly OATP1a/1b restrict its oral availability.

Sotorasib (Lumakras™) is the first FDA-approved KRASG12C inhibitor for treatment of patients with non-small cell lung cancer (NSCLC) carrying this mutation. Using genetically modified mouse models, we studied the influence of the efflux transporters ABCB1 and ABCG2, the OATP1a/1b uptake transporters, and the CYP3A drug-metabolizing enzyme complex on the plasma pharmacokinetics and tissue distribution of oral sotorasib. In vitro, sotorasib was a potent substrate for human ABCB1 and a modest substrate for mouse Abcg2, but not for human ABCG2. In vivo, the brain-to-plasma ratio of sotorasib (40 mg/kg) was highly increased in Abcb1a/1b-/- (5.9-fold) and Abcb1a/1b;Abcg2-/- (7.6-fold) compared to wild-type mice, but not in single Abcg2-/- mice. Upon coadministering elacridar, an ABCB1/ABCG2 inhibitor, sotorasib brain accumulation increased 7.5-fold, approaching the levels observed in Abcb1a/1b-deficient mice. No acute CNS toxicity emerged upon boosting of the sotorasib exposure. In Oatp1a/1b-deficient mice, we observed a 2-fold reduction in liver disposition compared to wild-type mice, although these uptake transporters had no noticeable impact on sotorasib plasma exposure. However, plasma exposure was limited by mouse Cyp3a and human CYP3A4, as the AUC0-4 h in Cyp3a-/- mice was increased by 2.5-fold compared to wild-type mice, and subsequently strongly decreased (by 3.9-fold) in Cyp3aXAV mice transgenically overexpressing human CYP3A4 in liver and intestine. Collectively, the oral availability of sotorasib was markedly limited by CYP3A and possibly also by ABCB1 and OATP1a/b, whereas its brain accumulation was strongly restricted by ABCB1. The obtained results may help to further optimize the safety and efficacy of sotorasib in clinical use.

EP300 knockdown reduces cancer stem cell phenotype, tumor growth and metastasis in triple negative breast cancer.

BACKGROUND: Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype with basal features, lacking the expression of receptors targeted successfully in other breast cancer subtypes. Treatment response to adjuvant and neoadjuvant chemotherapy is often short-lived and metastatic spread occurs at higher rates than other subtypes within the first five years after diagnosis. TNBCs exhibit stem cell features and are enriched for cancer stem cell (CSC) populations. E1A Binding Protein P300 (EP300) is a large protein with multiple cellular functions, including as an effector in stem cell biology. METHODS: We used a genetic knockdown (KD) model of EP300 in TNBC cell lines to investigate the effect on CSC phenotype, tumor growth and metastasis. Side population assay and tumorsphere suspension culture were used in vitro. Xenograft mouse models were used for in vivo studies. We performed in silico analysis of publicly available gene expression data sets to investigate CSC gene expression and molecular pathways as well as survival outcomes associated with EP300 expression in patients with TNBC and basal-like BC. RESULTS: EP300 KD abolished the CSC phenotype by reducing ABCG2 expression, side population cells and tumorsphere formation capacity in vitro as well as tumor formation in a xenograft mouse model in vivo. Metastatic capacity was markedly reduced in EP300 KD cells in vivo, with no detection of circulating tumor cells. TCGA data analysis demonstrated that genes positively correlated with EP300 expression in TNBC and basal-like BC were associated with CSC biology. Survival analysis demonstrated that EP300 expression predicts poor recurrence free survival in TNBC and basal BC. CONCLUSION: We report a novel oncogenic role for EP300 in driving CSC phenotype representing a potential target to address tumor initiation and metastatic spread in TNBC and basal-like BC. EP300 might serve as a prognostic marker and potential therapeutic target in TNBC.

Pharmacokinetics of the KRASG12C inhibitor adagrasib is limited by CYP3A and ABCB1, and influenced by binding to mouse plasma carboxylesterase 1c.

Adagrasib (Krazati™) is the second FDA-approved specific KRASG12C inhibitor for non-small cell lung cancer (NSCLC) patients harboring this mutation. The impact of the drug efflux transporters ABCB1 and ABCG2, and the drug-metabolizing enzymes CYP3A and carboxylesterase 1 (CES1) on the pharmacokinetics of oral adagrasib were studied using genetically modified mouse models. Adagrasib was potently transported by human ABCB1 and modestly by mouse Abcg2 in vitro. In Abcb1a/b-/- and Abcb1a/b;Abcg2-/- mice, the brain-to-plasma ratios were enhanced by 33- and 55-fold, respectively, compared to wild-type mice, whereas ratios in Abcg2-/- mice remained unchanged. The influence of ABC transporters was completely reversed by coadministration of the dual ABCB1/ABCG2 inhibitor elacridar, increasing the brain penetration in wild-type mice by 41-fold while no signs of acute CNS toxicity were observed. Tumor ABCB1 overexpression may thus confer adagrasib resistance. Whereas the ABC transporters did not affect adagrasib plasma exposure, CYP3A and Ces1 strongly impacted its apparent oral availability. The plasma AUC0-8 h was significantly enhanced by 2.3-fold in Cyp3a-/- compared to wild-type mice, and subsequently 4.3-fold reduced in transgenic CYP3A4 mice, indicating substantial CYP3A-mediated metabolism. Adagrasib plasma exposure was strongly reduced in Ces1-/- compared to wild-type mice, but tissue exposure was slightly increased, suggesting that adagrasib binds to plasma Ces1c in mice and is perhaps metabolized by Ces1. This binding could complicate interpretation of mouse studies, especially since humans lack circulating CES1 enzyme(s). Our results may be useful to further optimize the clinical safety and efficacy of adagrasib, and give more insight into potential drug-drug interactions risks.