The Experts below are selected from a list of 1905 Experts worldwide ranked by ideXlab platform
Ralph Tiedt - One of the best experts on this subject based on the ideXlab platform.
-
phase ib study of Ribociclib plus fulvestrant and Ribociclib plus fulvestrant plus pi3k inhibitor alpelisib or buparlisib for hr advanced breast cancer
Clinical Cancer Research, 2021Co-Authors: Sara M. Tolaney, Emiliano Calvo, Erika Paige Hamilton, Thomas Bachelot, Michela Maur, Angelica Fasolo, Ralph Tiedt, A Forerotorres, Lisa Nardi, Uz StammbergerAbstract:Purpose: Resistance to treatment with endocrine therapy in patients with HR+, HER2− advanced breast cancer (ABC) is common and dual inhibition of CDK4/6 and PI3K pathways may delay the development of resistance. This phase Ib trial evaluates the safety and tolerability of triple and double regimens containing the CDK4/6 inhibitor Ribociclib. Patients and Methods: In this open-label, multicenter, phase Ib study, 70 postmenopausal women with HR+, HER2− ABC were enrolled into one of four treatment combinations: Ribociclib (once daily, 3 weeks on, 1 week off) plus fulvestrant; Ribociclib (continuous dosing) plus fulvestrant; Ribociclib plus alpelisib plus fulvestrant; or Ribociclib plus buparlisib plus fulvestrant. Results: The recommended phase II dose (RP2D) of Ribociclib was confirmed to be 600 mg (3 weeks on, 1 week off) and 400 mg (continuous dosing) plus fulvestrant 500 mg. For the triple combination with buparlisib, the RP2D was Ribociclib 400 mg plus buparlisib 30 mg plus fulvestrant 500 mg. Enrollment for the triple combinations was stopped due to unexpected toxicity. No RP2D was determined for the alpelisib combination. The safety profiles of the Ribociclib plus fulvestrant combinations were consistent with those in previous studies. There was no marked difference in Ribociclib exposure in the presence of triple-combination partners. The highest overall response rate was seen in the buparlisib triple combination (25.0%; 95% confidence interval, 9.8–46.7). Conclusions: Ribociclib plus fulvestrant demonstrated safety in the treatment of patients with HR+, HER2− ABC. Triple combinations with alpelisib or buparlisib plus fulvestrant are not recommended for phase II investigation. See related commentary by Clark et al., p. 371
-
Phase Ib Study of Ribociclib plus Fulvestrant and Ribociclib plus Fulvestrant plus PI3K Inhibitor (Alpelisib or Buparlisib) for HR+ Advanced Breast Cancer.
Clinical cancer research : an official journal of the American Association for Cancer Research, 2020Co-Authors: Sara M. Tolaney, Emiliano Calvo, Erika Paige Hamilton, Andres Forero-torres, Thomas Bachelot, Michela Maur, Angelica Fasolo, Ralph TiedtAbstract:Purpose Resistance to treatment with endocrine therapy in patients with HR+, HER2- advanced breast cancer (ABC) is common and dual inhibition of CDK4/6 and PI3K pathways may delay the development of resistance. This phase Ib trial evaluates the safety and tolerability of triple and double regimens containing the CDK4/6 inhibitor Ribociclib. Experimental design In this open-label, multicenter, phase Ib study, 70 postmenopausal women with HR+, HER2- ABC were enrolled into one of four treatment combinations: Ribociclib (once daily, 3 weeks on, 1 week off) plus fulvestrant; Ribociclib (continuous dosing) plus fulvestrant; Ribociclib plus alpelisib plus fulvestrant; or Ribociclib plus buparlisib plus fulvestrant. Results The recommended phase II dose (RP2D) of Ribociclib was confirmed to be 600 mg (3 weeks on, 1 week off) and 400 mg (continuous dosing) plus fulvestrant 500 mg. For the triple combination with buparlisib, the RP2D was Ribociclib 400 mg plus buparlisib 30 mg plus fulvestrant 500 mg. Enrollment for the triple combinations was stopped due to unexpected toxicity. No RP2D was determined for the alpelisib combination. The safety profiles of the Ribociclib plus fulvestrant combinations were consistent with those in previous studies. There was no marked difference in Ribociclib exposure in the presence of triple combination partners. The highest overall response rate was seen in the buparlisib triple combination (25.0%, 95% confidence interval, 9.8-46.7%). Conclusions Ribociclib plus fulvestrant demonstrated safety in the treatment of patients with HR+, HER2- ABC. Triple combinations with alpelisib or buparlisib plus fulvestrant are not recommended for phase II investigation. NCT02088684.
-
the potent and selective cyclin dependent kinases 4 and 6 inhibitor Ribociclib lee011 is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria PinzonortizAbstract:Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
The potent and selective cyclin-dependent kinases 4 and 6 inhibitor Ribociclib (LEE011) is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria Pinzon-ortizAbstract:// Sunkyu Kim 1 , Ralph Tiedt 2 , Alice Loo 1 , Thomas Horn 1 , Scott Delach 1 , Steven Kovats 1 , Kristy Haas 1 , Barbara Schacher Engstler 2 , Alexander Cao 1 , Maria Pinzon-Ortiz 1 , Iain Mulford 1 , Michael G. Acker 1 , Rajiv Chopra 3 , Christopher Brain 4 , Emmanuelle di Tomaso 1 , William R. Sellers 1 and Giordano Caponigro 1 1 Novartis Institutes for BioMedical Research, Oncology Disease Area, Cambridge, MA, USA 2 Novartis Institutes for BioMedical Research, Oncology Disease Area, Basel, Switzerland, USA 3 Novartis Institutes for BioMedical Research, Chemical Biology & Therapeutics, Cambridge, MA, USA 4 Novartis Institutes for BioMedical Research, Global Discovery Chemistry, Cambridge, MA, USA Correspondence to: Giordano Caponigro, email: giordano.caponigro@novartis.com Keywords: CDK4/6 inhibitor; Ribociclib; LEE011; preclinical; selectivity Received: May 22, 2018 Accepted: September 15, 2018 Published: October 16, 2018 ABSTRACT Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4 -dependent cells than in CDK6 -dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
Abstract 2346: Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib
Molecular and Cellular Biology Genetics, 2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards a cell’s entry into S phase by binding E2F transcription factors and keeping them inactive. Many growth-promoting stimuli increase expression of D-type cyclins, which bind to and activate cyclin-dependent kinases 4 and 6 (CDK4/6). The cyclin D–bound CDK4/6 holoenzymes phosphorylate Rb, resulting in release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6–Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA breakthrough therapy and priority review designations for treatment of hormone receptor–positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here we describe the preclinical selectivity profile of Ribociclib in biochemical and cellular assays. Ribociclib inhibits both CDK4–cyclin D1 and CDK6–cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address the selectivity of Ribociclib in direct comparison with 2 other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KINOMEscan assay consisting of >450 kinase active site–directed competition-binding assays. We adjusted the test concentrations in the kinase-selectivity panel per the binding constants for CDK4 and CDK6 to account for the higher potency of abemaciclib. Data showed that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel), with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the 3 inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measured metabolic activity (eg, CTG) tended to underestimate the effects of CDK4/6 inhibition; thus, assays that either directly or indirectly assessed cell number were used instead. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA or CRISPR-based functional assays. When determining IC50s of the 3 CDK4/6 inhibitors in these cell lines, we found that Ribociclib and abemaciclib demonstrated greater activity in CDK4-dependent cells vs CDK6-dependent cells, whereas palbociclib was similarly active in both cell types. The high degree of CDK4 selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4. Citation Format: Ralph Tiedt, Scott Delach, Steven Kovats, Thomas Horn, Michael Acker, Barbara Schacher Engstler, Giordano Caponigro, Fei Su. Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2346. doi:10.1158/1538-7445.AM2017-2346
Barbara Schacher Engstler - One of the best experts on this subject based on the ideXlab platform.
-
the potent and selective cyclin dependent kinases 4 and 6 inhibitor Ribociclib lee011 is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria PinzonortizAbstract:Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
The potent and selective cyclin-dependent kinases 4 and 6 inhibitor Ribociclib (LEE011) is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria Pinzon-ortizAbstract:// Sunkyu Kim 1 , Ralph Tiedt 2 , Alice Loo 1 , Thomas Horn 1 , Scott Delach 1 , Steven Kovats 1 , Kristy Haas 1 , Barbara Schacher Engstler 2 , Alexander Cao 1 , Maria Pinzon-Ortiz 1 , Iain Mulford 1 , Michael G. Acker 1 , Rajiv Chopra 3 , Christopher Brain 4 , Emmanuelle di Tomaso 1 , William R. Sellers 1 and Giordano Caponigro 1 1 Novartis Institutes for BioMedical Research, Oncology Disease Area, Cambridge, MA, USA 2 Novartis Institutes for BioMedical Research, Oncology Disease Area, Basel, Switzerland, USA 3 Novartis Institutes for BioMedical Research, Chemical Biology & Therapeutics, Cambridge, MA, USA 4 Novartis Institutes for BioMedical Research, Global Discovery Chemistry, Cambridge, MA, USA Correspondence to: Giordano Caponigro, email: giordano.caponigro@novartis.com Keywords: CDK4/6 inhibitor; Ribociclib; LEE011; preclinical; selectivity Received: May 22, 2018 Accepted: September 15, 2018 Published: October 16, 2018 ABSTRACT Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4 -dependent cells than in CDK6 -dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
Abstract 2346: Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib
Molecular and Cellular Biology Genetics, 2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards a cell’s entry into S phase by binding E2F transcription factors and keeping them inactive. Many growth-promoting stimuli increase expression of D-type cyclins, which bind to and activate cyclin-dependent kinases 4 and 6 (CDK4/6). The cyclin D–bound CDK4/6 holoenzymes phosphorylate Rb, resulting in release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6–Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA breakthrough therapy and priority review designations for treatment of hormone receptor–positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here we describe the preclinical selectivity profile of Ribociclib in biochemical and cellular assays. Ribociclib inhibits both CDK4–cyclin D1 and CDK6–cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address the selectivity of Ribociclib in direct comparison with 2 other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KINOMEscan assay consisting of >450 kinase active site–directed competition-binding assays. We adjusted the test concentrations in the kinase-selectivity panel per the binding constants for CDK4 and CDK6 to account for the higher potency of abemaciclib. Data showed that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel), with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the 3 inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measured metabolic activity (eg, CTG) tended to underestimate the effects of CDK4/6 inhibition; thus, assays that either directly or indirectly assessed cell number were used instead. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA or CRISPR-based functional assays. When determining IC50s of the 3 CDK4/6 inhibitors in these cell lines, we found that Ribociclib and abemaciclib demonstrated greater activity in CDK4-dependent cells vs CDK6-dependent cells, whereas palbociclib was similarly active in both cell types. The high degree of CDK4 selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4. Citation Format: Ralph Tiedt, Scott Delach, Steven Kovats, Thomas Horn, Michael Acker, Barbara Schacher Engstler, Giordano Caponigro, Fei Su. Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2346. doi:10.1158/1538-7445.AM2017-2346
-
Pre-clinical Selectivity Profile of the CDK4/6 Inhibitor Ribociclib Compared With That of Palbociclib and Abemaciclib
2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards the entry point into S phase by binding E2F transcription factors and keeping them inactive. Many growth promoting stimuli increase the expression of D-cyclins, which bind to and activate CDK4/6 kinases. The D-cyclin bound CDK4/6 holoenzymes phosphorylate Rb resulting in the release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6-Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA Breakthrough designation and Priority Review for treatment of hormone receptor positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here, we describe the pre-clinical selectivity profile of Ribociclib in biochemical and cellular assay. Ribociclib inhibits both CDK4 - cyclin D1 and CDK6 - cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address selectivity of Ribociclib in direct comparison with two other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KinomeScan assay platform (DiscoverX) consisting of >450 kinase active site-directed competition binding assays. Based on the binding constants (Kd) for CDK4 and CDK6, we adjusted the test concentrations in the kinase selectivity panel to account for higher potency of abemaciclib. Data indicated that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel) with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the three inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measure metabolic activity (such as CTG) tend to underestimate the effects of CDK4/6 inhibition. Therefore, assays that either directly or indirectly assessed cell number were used in these studies. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA/CRISPR-based functional assays. When determining IC50 values for these cell lines with the three CDK4/6 inhibitors, we found that both Ribociclib and abemaciclib demonstrated greater activity in CDK4-relative to CDK6-dependent cells, whereas palbociclib was similarly active in both cells types. In conclusion, the high degree of selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4.
Steven Kovats - One of the best experts on this subject based on the ideXlab platform.
-
the potent and selective cyclin dependent kinases 4 and 6 inhibitor Ribociclib lee011 is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria PinzonortizAbstract:Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
The potent and selective cyclin-dependent kinases 4 and 6 inhibitor Ribociclib (LEE011) is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria Pinzon-ortizAbstract:// Sunkyu Kim 1 , Ralph Tiedt 2 , Alice Loo 1 , Thomas Horn 1 , Scott Delach 1 , Steven Kovats 1 , Kristy Haas 1 , Barbara Schacher Engstler 2 , Alexander Cao 1 , Maria Pinzon-Ortiz 1 , Iain Mulford 1 , Michael G. Acker 1 , Rajiv Chopra 3 , Christopher Brain 4 , Emmanuelle di Tomaso 1 , William R. Sellers 1 and Giordano Caponigro 1 1 Novartis Institutes for BioMedical Research, Oncology Disease Area, Cambridge, MA, USA 2 Novartis Institutes for BioMedical Research, Oncology Disease Area, Basel, Switzerland, USA 3 Novartis Institutes for BioMedical Research, Chemical Biology & Therapeutics, Cambridge, MA, USA 4 Novartis Institutes for BioMedical Research, Global Discovery Chemistry, Cambridge, MA, USA Correspondence to: Giordano Caponigro, email: giordano.caponigro@novartis.com Keywords: CDK4/6 inhibitor; Ribociclib; LEE011; preclinical; selectivity Received: May 22, 2018 Accepted: September 15, 2018 Published: October 16, 2018 ABSTRACT Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4 -dependent cells than in CDK6 -dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
Abstract 2346: Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib
Molecular and Cellular Biology Genetics, 2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards a cell’s entry into S phase by binding E2F transcription factors and keeping them inactive. Many growth-promoting stimuli increase expression of D-type cyclins, which bind to and activate cyclin-dependent kinases 4 and 6 (CDK4/6). The cyclin D–bound CDK4/6 holoenzymes phosphorylate Rb, resulting in release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6–Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA breakthrough therapy and priority review designations for treatment of hormone receptor–positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here we describe the preclinical selectivity profile of Ribociclib in biochemical and cellular assays. Ribociclib inhibits both CDK4–cyclin D1 and CDK6–cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address the selectivity of Ribociclib in direct comparison with 2 other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KINOMEscan assay consisting of >450 kinase active site–directed competition-binding assays. We adjusted the test concentrations in the kinase-selectivity panel per the binding constants for CDK4 and CDK6 to account for the higher potency of abemaciclib. Data showed that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel), with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the 3 inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measured metabolic activity (eg, CTG) tended to underestimate the effects of CDK4/6 inhibition; thus, assays that either directly or indirectly assessed cell number were used instead. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA or CRISPR-based functional assays. When determining IC50s of the 3 CDK4/6 inhibitors in these cell lines, we found that Ribociclib and abemaciclib demonstrated greater activity in CDK4-dependent cells vs CDK6-dependent cells, whereas palbociclib was similarly active in both cell types. The high degree of CDK4 selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4. Citation Format: Ralph Tiedt, Scott Delach, Steven Kovats, Thomas Horn, Michael Acker, Barbara Schacher Engstler, Giordano Caponigro, Fei Su. Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2346. doi:10.1158/1538-7445.AM2017-2346
-
Pre-clinical Selectivity Profile of the CDK4/6 Inhibitor Ribociclib Compared With That of Palbociclib and Abemaciclib
2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards the entry point into S phase by binding E2F transcription factors and keeping them inactive. Many growth promoting stimuli increase the expression of D-cyclins, which bind to and activate CDK4/6 kinases. The D-cyclin bound CDK4/6 holoenzymes phosphorylate Rb resulting in the release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6-Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA Breakthrough designation and Priority Review for treatment of hormone receptor positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here, we describe the pre-clinical selectivity profile of Ribociclib in biochemical and cellular assay. Ribociclib inhibits both CDK4 - cyclin D1 and CDK6 - cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address selectivity of Ribociclib in direct comparison with two other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KinomeScan assay platform (DiscoverX) consisting of >450 kinase active site-directed competition binding assays. Based on the binding constants (Kd) for CDK4 and CDK6, we adjusted the test concentrations in the kinase selectivity panel to account for higher potency of abemaciclib. Data indicated that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel) with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the three inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measure metabolic activity (such as CTG) tend to underestimate the effects of CDK4/6 inhibition. Therefore, assays that either directly or indirectly assessed cell number were used in these studies. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA/CRISPR-based functional assays. When determining IC50 values for these cell lines with the three CDK4/6 inhibitors, we found that both Ribociclib and abemaciclib demonstrated greater activity in CDK4-relative to CDK6-dependent cells, whereas palbociclib was similarly active in both cells types. In conclusion, the high degree of selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4.
Scott Delach - One of the best experts on this subject based on the ideXlab platform.
-
the potent and selective cyclin dependent kinases 4 and 6 inhibitor Ribociclib lee011 is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria PinzonortizAbstract:Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
The potent and selective cyclin-dependent kinases 4 and 6 inhibitor Ribociclib (LEE011) is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria Pinzon-ortizAbstract:// Sunkyu Kim 1 , Ralph Tiedt 2 , Alice Loo 1 , Thomas Horn 1 , Scott Delach 1 , Steven Kovats 1 , Kristy Haas 1 , Barbara Schacher Engstler 2 , Alexander Cao 1 , Maria Pinzon-Ortiz 1 , Iain Mulford 1 , Michael G. Acker 1 , Rajiv Chopra 3 , Christopher Brain 4 , Emmanuelle di Tomaso 1 , William R. Sellers 1 and Giordano Caponigro 1 1 Novartis Institutes for BioMedical Research, Oncology Disease Area, Cambridge, MA, USA 2 Novartis Institutes for BioMedical Research, Oncology Disease Area, Basel, Switzerland, USA 3 Novartis Institutes for BioMedical Research, Chemical Biology & Therapeutics, Cambridge, MA, USA 4 Novartis Institutes for BioMedical Research, Global Discovery Chemistry, Cambridge, MA, USA Correspondence to: Giordano Caponigro, email: giordano.caponigro@novartis.com Keywords: CDK4/6 inhibitor; Ribociclib; LEE011; preclinical; selectivity Received: May 22, 2018 Accepted: September 15, 2018 Published: October 16, 2018 ABSTRACT Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4 -dependent cells than in CDK6 -dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
Abstract 2346: Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib
Molecular and Cellular Biology Genetics, 2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards a cell’s entry into S phase by binding E2F transcription factors and keeping them inactive. Many growth-promoting stimuli increase expression of D-type cyclins, which bind to and activate cyclin-dependent kinases 4 and 6 (CDK4/6). The cyclin D–bound CDK4/6 holoenzymes phosphorylate Rb, resulting in release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6–Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA breakthrough therapy and priority review designations for treatment of hormone receptor–positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here we describe the preclinical selectivity profile of Ribociclib in biochemical and cellular assays. Ribociclib inhibits both CDK4–cyclin D1 and CDK6–cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address the selectivity of Ribociclib in direct comparison with 2 other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KINOMEscan assay consisting of >450 kinase active site–directed competition-binding assays. We adjusted the test concentrations in the kinase-selectivity panel per the binding constants for CDK4 and CDK6 to account for the higher potency of abemaciclib. Data showed that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel), with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the 3 inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measured metabolic activity (eg, CTG) tended to underestimate the effects of CDK4/6 inhibition; thus, assays that either directly or indirectly assessed cell number were used instead. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA or CRISPR-based functional assays. When determining IC50s of the 3 CDK4/6 inhibitors in these cell lines, we found that Ribociclib and abemaciclib demonstrated greater activity in CDK4-dependent cells vs CDK6-dependent cells, whereas palbociclib was similarly active in both cell types. The high degree of CDK4 selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4. Citation Format: Ralph Tiedt, Scott Delach, Steven Kovats, Thomas Horn, Michael Acker, Barbara Schacher Engstler, Giordano Caponigro, Fei Su. Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2346. doi:10.1158/1538-7445.AM2017-2346
-
Pre-clinical Selectivity Profile of the CDK4/6 Inhibitor Ribociclib Compared With That of Palbociclib and Abemaciclib
2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards the entry point into S phase by binding E2F transcription factors and keeping them inactive. Many growth promoting stimuli increase the expression of D-cyclins, which bind to and activate CDK4/6 kinases. The D-cyclin bound CDK4/6 holoenzymes phosphorylate Rb resulting in the release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6-Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA Breakthrough designation and Priority Review for treatment of hormone receptor positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here, we describe the pre-clinical selectivity profile of Ribociclib in biochemical and cellular assay. Ribociclib inhibits both CDK4 - cyclin D1 and CDK6 - cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address selectivity of Ribociclib in direct comparison with two other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KinomeScan assay platform (DiscoverX) consisting of >450 kinase active site-directed competition binding assays. Based on the binding constants (Kd) for CDK4 and CDK6, we adjusted the test concentrations in the kinase selectivity panel to account for higher potency of abemaciclib. Data indicated that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel) with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the three inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measure metabolic activity (such as CTG) tend to underestimate the effects of CDK4/6 inhibition. Therefore, assays that either directly or indirectly assessed cell number were used in these studies. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA/CRISPR-based functional assays. When determining IC50 values for these cell lines with the three CDK4/6 inhibitors, we found that both Ribociclib and abemaciclib demonstrated greater activity in CDK4-relative to CDK6-dependent cells, whereas palbociclib was similarly active in both cells types. In conclusion, the high degree of selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4.
Thomas Horn - One of the best experts on this subject based on the ideXlab platform.
-
the potent and selective cyclin dependent kinases 4 and 6 inhibitor Ribociclib lee011 is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria PinzonortizAbstract:Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4-dependent cells than in CDK6-dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
The potent and selective cyclin-dependent kinases 4 and 6 inhibitor Ribociclib (LEE011) is a versatile combination partner in preclinical cancer models
Oncotarget, 2018Co-Authors: Sunkyu Kim, Ralph Tiedt, Alice Loo, Thomas Horn, Scott Delach, Steven Kovats, Kristy Haas, Barbara Schacher Engstler, Alexander Cao, Maria Pinzon-ortizAbstract:// Sunkyu Kim 1 , Ralph Tiedt 2 , Alice Loo 1 , Thomas Horn 1 , Scott Delach 1 , Steven Kovats 1 , Kristy Haas 1 , Barbara Schacher Engstler 2 , Alexander Cao 1 , Maria Pinzon-Ortiz 1 , Iain Mulford 1 , Michael G. Acker 1 , Rajiv Chopra 3 , Christopher Brain 4 , Emmanuelle di Tomaso 1 , William R. Sellers 1 and Giordano Caponigro 1 1 Novartis Institutes for BioMedical Research, Oncology Disease Area, Cambridge, MA, USA 2 Novartis Institutes for BioMedical Research, Oncology Disease Area, Basel, Switzerland, USA 3 Novartis Institutes for BioMedical Research, Chemical Biology & Therapeutics, Cambridge, MA, USA 4 Novartis Institutes for BioMedical Research, Global Discovery Chemistry, Cambridge, MA, USA Correspondence to: Giordano Caponigro, email: giordano.caponigro@novartis.com Keywords: CDK4/6 inhibitor; Ribociclib; LEE011; preclinical; selectivity Received: May 22, 2018 Accepted: September 15, 2018 Published: October 16, 2018 ABSTRACT Inhibition of cyclin-dependent kinases 4 and 6 (CDK4/6) is associated with robust antitumor activity. Ribociclib (LEE011) is an orally bioavailable CDK4/6 inhibitor that is approved for the treatment of hormone receptor–positive, human epidermal growth factor receptor 2–negative advanced breast cancer, in combination with an aromatase inhibitor, and is currently being evaluated in several additional trials. Here, we report the preclinical profile of Ribociclib. When tested across a large panel of kinase active site binding assays, Ribociclib and palbociclib were highly selective for CDK4, while abemaciclib showed affinity to several other kinases. Both Ribociclib and abemaciclib showed slightly higher potency in CDK4 -dependent cells than in CDK6 -dependent cells, while palbociclib did not show such a difference. Profiling CDK4/6 inhibitors in large-scale cancer cell line screens in vitro confirmed that RB1 loss of function is a negative predictor of sensitivity. We also found that routinely used cellular viability assays measuring adenosine triphosphate levels as a proxy for cell numbers underestimated the effects of CDK4/6 inhibition, which contrasts with assays that assess cell number more directly. Robust antitumor efficacy and combination benefit was detected when Ribociclib was added to encorafenib, nazartinib, or endocrine therapies in patient-derived xenografts.
-
Abstract 2346: Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib
Molecular and Cellular Biology Genetics, 2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards a cell’s entry into S phase by binding E2F transcription factors and keeping them inactive. Many growth-promoting stimuli increase expression of D-type cyclins, which bind to and activate cyclin-dependent kinases 4 and 6 (CDK4/6). The cyclin D–bound CDK4/6 holoenzymes phosphorylate Rb, resulting in release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6–Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA breakthrough therapy and priority review designations for treatment of hormone receptor–positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here we describe the preclinical selectivity profile of Ribociclib in biochemical and cellular assays. Ribociclib inhibits both CDK4–cyclin D1 and CDK6–cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address the selectivity of Ribociclib in direct comparison with 2 other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KINOMEscan assay consisting of >450 kinase active site–directed competition-binding assays. We adjusted the test concentrations in the kinase-selectivity panel per the binding constants for CDK4 and CDK6 to account for the higher potency of abemaciclib. Data showed that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel), with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the 3 inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measured metabolic activity (eg, CTG) tended to underestimate the effects of CDK4/6 inhibition; thus, assays that either directly or indirectly assessed cell number were used instead. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA or CRISPR-based functional assays. When determining IC50s of the 3 CDK4/6 inhibitors in these cell lines, we found that Ribociclib and abemaciclib demonstrated greater activity in CDK4-dependent cells vs CDK6-dependent cells, whereas palbociclib was similarly active in both cell types. The high degree of CDK4 selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4. Citation Format: Ralph Tiedt, Scott Delach, Steven Kovats, Thomas Horn, Michael Acker, Barbara Schacher Engstler, Giordano Caponigro, Fei Su. Preclinical selectivity profile of the CDK4/6 inhibitor Ribociclib (LEE011) compared with that of palbociclib and abemaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2346. doi:10.1158/1538-7445.AM2017-2346
-
Pre-clinical Selectivity Profile of the CDK4/6 Inhibitor Ribociclib Compared With That of Palbociclib and Abemaciclib
2017Co-Authors: Ralph Tiedt, Thomas Horn, Scott Delach, Steven Kovats, Barbara Schacher Engstler, Michael G. Acker, Giordano CaponigroAbstract:A hallmark of cancer is unchecked cell division. Retinoblastoma protein (Rb) is a human tumor suppressor that guards the entry point into S phase by binding E2F transcription factors and keeping them inactive. Many growth promoting stimuli increase the expression of D-cyclins, which bind to and activate CDK4/6 kinases. The D-cyclin bound CDK4/6 holoenzymes phosphorylate Rb resulting in the release of E2F, which in turn activates genes required for S phase entry and DNA replication. Numerous oncogenic aberrations converge at the CDK4/6-Rb pathway, providing a strong rationale for developing CDK4/6 inhibitors as cancer therapeutics. Ribociclib (LEE011) is a selective CDK4/6 inhibitor that has received FDA Breakthrough designation and Priority Review for treatment of hormone receptor positive breast cancer in combination with letrozole and is being tested in additional clinical trials. Here, we describe the pre-clinical selectivity profile of Ribociclib in biochemical and cellular assay. Ribociclib inhibits both CDK4 - cyclin D1 and CDK6 - cyclin D3 kinase activity with nanomolar IC50s in biochemical assays. To comprehensively address selectivity of Ribociclib in direct comparison with two other clinical CDK4/6 inhibitors, palbociclib and abemaciclib, we made use of the KinomeScan assay platform (DiscoverX) consisting of >450 kinase active site-directed competition binding assays. Based on the binding constants (Kd) for CDK4 and CDK6, we adjusted the test concentrations in the kinase selectivity panel to account for higher potency of abemaciclib. Data indicated that both Ribociclib and palbociclib have high selectivity for CDK4 (CDK6 was not covered in the panel) with very few distinct additional binding events detected. In contrast, abemaciclib is a much more promiscuous kinase inhibitor. Next, we sought to determine the relative potencies of the three inhibitors against CDK4 vs CDK6 in cellular assays. When testing different routinely used readouts of cellular viability, we found that assays that measure metabolic activity (such as CTG) tend to underestimate the effects of CDK4/6 inhibition. Therefore, assays that either directly or indirectly assessed cell number were used in these studies. We first identified cancer cell lines primarily dependent on either CDK4 or CDK6 as judged by combined RNA expression analysis and shRNA/CRISPR-based functional assays. When determining IC50 values for these cell lines with the three CDK4/6 inhibitors, we found that both Ribociclib and abemaciclib demonstrated greater activity in CDK4-relative to CDK6-dependent cells, whereas palbociclib was similarly active in both cells types. In conclusion, the high degree of selectivity of Ribociclib suggests that off-target kinase inhibition is an unlikely complication in patients. Moreover, the apparent preference for CDK4 over CDK6 could be an advantage in certain cancer types that are primarily dependent on CDK4.
