CDK4/6

In the plasma of healthy persons, the metabolite M18 hydrochloride of abelacilb has a T1/2 of 43.1 hours [3]. The primary mode of action of CDK4/6 inhibitors is to cause cell cycle arrest by blocking the phosphorylation of the retinoblastoma (RB) protein. Other modifications to cancer cell biology are made by CDK4/6 inhibitors [4].

CDK4/6 inhibitors enhanced T cell survival and immunological memory in mice given tumor-specific CD8+ T cells [5].

[1]. Abemaciclib in Combination with Single-Agent Options in Patients with Stage IV Non–Small Cell Lung Cancer: A Phase Ib Study. Clin Cancer Res (2018) 24 (22): 5543–5551.

[2]. Degradation of cyclin-dependent kinase 4/6 (cdk4/6) by conjugation of cdk4/6 inhibitors with e3 ligase ligand and methods of use. WO2017185031A1.

[3]. Abstract CT153: Pharmacokinetic drug interactions between abemaciclib and CYP3A inducers and inhibitors. Cancer Res. 2016-7-15; 76 (14_Supplement): CT153.

[4]. CDK4/6 Inhibition in Cancer: Beyond Cell Cycle Arrest. Trends Cell Biol. 2018 Nov;28(11):911-925.

[5]. Inhibition of CDK4/6 Promotes CD8 T-cell Memory Formation. Cancer Discov. 2021 Oct;11(10):2564-2581.

Purpose: Abemaciclib, a dual inhibitor of cyclin-dependent kinases 4 and 6, has demonstrated preclinical activity in non–small cell lung cancer (NSCLC). A multicenter, nonrandomized, open-label phase Ib study was conducted to test safety, MTD, pharmacokinetics, and preliminary antitumor activity of abemaciclib in combination with other therapies for treatment in patients with metastatic NSCLC. Patients and Methods: An initial dose escalation phase was used to determine the MTD of twice-daily oral abemaciclib (150, 200 mg) plus pemetrexed, gemcitabine, or ramucirumab, followed by an expansion phase for each drug combination. Pemetrexed and gemcitabine were administered according to label. The abemaciclib plus ramucirumab study examined two dosing schedules. Results: The three study parts enrolled 86 patients; all received ≥1 dose of combination therapy. Across arms, the most common treatment-emergent adverse events were fatigue, diarrhea, neutropenia, decreased appetite, and nausea. The trial did not identify an abemaciclib MTD for the combination with pemetrexed or gemcitabine but did so for the combination of abemaciclib with days 1 and 8 ramucirumab (8 mg/kg). Plasma sample analysis showed that abemaciclib did not influence the pharmacokinetics of the combination agents and the combination agents did not affect abemaciclib exposure. The disease control rate was 57% for patients treated with abemaciclib–pemetrexed, 25% for abemaciclib–gemcitabine, and 54% for abemaciclib–ramucirumab. Median progression-free survival was 5.55, 1.58, and 4.83 months, respectively. Conclusions: Abemaciclib demonstrated an acceptable safety profile when dosed on a continuous twice-daily schedule in combination with pemetrexed, gemcitabine, or ramucirumab. Abemaciclib exposures remained consistent with those observed in single-agent studies. [1]

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Abemaciclib is a selective and potent small-molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6) being investigated for treatment of refractory hormone-receptor positive (HR+) advanced or metastatic breast cancer. In vitro, CYP3A is responsible for >99% of the CYP-mediated microsomal metabolism of abemaciclib and its active metabolites. Three clinical studies evaluated the disposition and metabolism and drug interaction potential of abemaciclib in the presence of a strong CYP3A-inducer, rifampin, or a strong CYP3A-inhibitor, clarithromycin. Abemaciclib disposition and metabolism were determined following a single oral 150 mg dose of [14C]-abemaciclib in healthy subjects (N = 6). In the rifampin interaction study, abemaciclib was administered as a single oral 200 mg dose in healthy subjects (N = 24) on 2 occasions: alone on Day 1 of Period 1 and in combination with 600 mg rifampin on Day 7 of Period 2, after 6 days of rifampin once daily (QD) dosing; rifampin continued QD for 7 days after abemaciclib. In the clarithromycin interaction study, abemaciclib was administered as a single oral 50 mg dose in patients with advanced cancer (N = 26) on 2 occasions: alone in Period 1 and on Day 5 of clarithromycin dosing (500 mg BID) in Period 2 followed by an additional 7 days of clarithromycin. Abemaciclib was extensively metabolized, with less than 10% of parent drug recovered unchanged in feces. Parent drug and 3 active metabolites; (LSN2839567 [M2], LSN3106729 [M18], and LSN3106726 [M20]) were detected in plasma. The mean t1/2 in healthy subjects was 29.0, 104.0, 55.9, and 43.1 hours for abemaciclib, M2, M18, and M20, respectively. Coadministration with rifampin compared to abemaciclib alone decreased abemaciclib AUC(0-?) and Cmax by 95% and 92%, respectively, and decreased AUC(0-?) and Cmax of total active species (abemaciclib + M2 + M18+ M20) by 77% and 45%, respectively. Coadministration with clarithromycin compared to abemaciclib alone increased abemaciclib AUC(0-?) and Cmax by 237% and 30%, respectively; and increased the total active species AUC(0-?) by 119% and decreased Cmax by 7%. The mean abemaciclib t1/2 was prolonged from 28.8 to 63.6 hours. No clinically significant safety concerns were observed following single doses of abemaciclib in healthy subjects or in patients with advanced cancer based on vital signs, clinical laboratory evaluations, and electrocardiogram data. The human absorption, distribution, metabolism and excretion study indicated that abemaciclib was cleared primarily by hepatic metabolism, and the clinical drug-drug interaction studies with strong CYP3A inducer and inhibitor substantiated the major role of CYP3A in the metabolism of abemaciclib. Due to significant changes in abemaciclib and active-metabolite exposure in the presence of strong CYP3A inducers and inhibitors, concomitant use with abemaciclib should be avoided, or abemaciclib dose may require adjustment. [3]

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Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have recently entered the therapeutic armamentarium of clinical oncologists, and show promising activity in patients with breast and other cancers. Although their chief mechanism of action is inhibition of retinoblastoma (RB) protein phosphorylation and thus the induction of cell cycle arrest, CDK4/6 inhibitors alter cancer cell biology in other ways that can also be leveraged for therapeutic benefit. These include modulation of mitogenic kinase signaling, induction of a senescence-like phenotype, and enhancement of cancer cell immunogenicity. We describe here the less-appreciated effects of CDK4/6 inhibitors on cancer cells, and suggest ways by which they might be exploited to enhance the benefits of these agents for cancer patients. [4]

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CDK4/6 inhibitors are approved to treat breast cancer and are in trials for other malignancies. We examined CDK4/6 inhibition in mouse and human CD8+ T cells during early stages of activation. Mice receiving tumor-specific CD8+ T cells treated with CDK4/6 inhibitors displayed increased T-cell persistence and immunologic memory. CDK4/6 inhibition upregulated MXD4, a negative regulator of MYC, in both mouse and human CD8+ T cells. Silencing of Mxd4 or Myc in mouse CD8+ T cells demonstrated the importance of this axis for memory formation. We used single-cell transcriptional profiling and T-cell receptor clonotype tracking to evaluate recently activated human CD8+ T cells in patients with breast cancer before and during treatment with either palbociclib or abemaciclib. CDK4/6 inhibitor therapy in humans increases the frequency of CD8+ memory precursors and downregulates their expression of MYC target genes, suggesting that CDK4/6 inhibitors in patients with cancer may augment long-term protective immunity. SIGNIFICANCE: CDK4/6 inhibition skews newly activated CD8+ T cells toward a memory phenotype in mice and humans with breast cancer. CDK4/6 inhibitors may have broad utility outside breast cancer, particularly in the neoadjuvant setting to augment CD8+ T-cell priming to tumor antigens prior to dosing with checkpoint blockade.This article is highlighted in the In This Issue feature, p. 2355.[5]

C25H29CLF2N8O

531.000570058823

530.212

2704316-82-3

Abemaciclib metabolite M18-d8;Abemaciclib metabolite M18;2704316-81-2

145925653

Off-white to light yellow solid powder

4

10

7

37

701

0

WGFYSOPSZMTSSV-UHFFFAOYSA-N

InChI=1S/C25H28F2N8O.ClH/c1-15(2)35-20-10-17(9-18(26)24(20)32-22(35)14-36)23-19(27)12-30-25(33-23)31-21-4-3-16(11-29-21)13-34-7-5-28-6-8-34;/h3-4,9-12,15,28,36H,5-8,13-14H2,1-2H3,(H,29,30,31,33);1H

[4-fluoro-6-[5-fluoro-2-[[5-(piperazin-1-ylmethyl)pyridin-2-yl]amino]pyrimidin-4-yl]-1-propan-2-ylbenzimidazol-2-yl]methanol;hydrochloride

Abemaciclib metabolite M18 hydrochloride; 2704316-82-3; Abemaciclib metabolite M18 (hydrochloride); LSN3106729 (hydrochloride); EX-A8463; CDK ligand for PROTAC hydrochloride;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 125 mg/mL (235.40 mM)
H2O : 100 mg/mL (188.32 mM)

Solubility in Formulation 1: 50 mg/mL (94.16 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with sonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)