Lack of access to CDK4/6 inhibitors for premenopausal patients with metastatic breast cancer in Brazil: estimation of the number of premature deaths

Purpose

A CDK4/6 inhibitor (CDK4/6i) combined with endocrine therapy is the standard of care for patients with hormone receptor-positive (HR+) and HER2-negative (HER2-) metastatic breast cancer (MBC). However, the incorporation of these agents into clinical practice remains challenging. This study aims to estimate the impact of the lack of access to ribociclib on mortality of premenopausal patients with MBC in Brazil.

Methods

Based on published epidemiological studies and national cancer registries, we estimated the number of premenopausal patients with potential indication of ribociclib as first-line treatment for MBC. Efficacy estimates were based on results from the Monaleesa-7 trial. Our analysis is made under the unrealistic assumption that all premenopausal MBC patients would be candidates for the treatment. To estimate the number of yearly premature deaths that could be prevented, we considered the largest absolute effect on mortality when sequentially applying the observed hazard ratio.

Results

We estimated an annual incidence of 4,294 premenopausal HR+, HER2- MBC patients in Brazil. Considering these patients, at 12, 24 and 60 months, the number of surviving subjects would be 3,504, 2,859 and 1,553 for endocrine therapy (ET) alone; and 3,717, 3,217 and 2,086 for ET plus ribociclib. The largest difference between both groups was observed at the end of the sixth year when the use of ribociclib would prevent 538 premature deaths (survival of 1,805 versus 1,267 patients by the 72nd month).

Conclusion

We estimate that lack of access to CDK4/6i for patients with HR+, HER2-, MBC will cause the premature death of a significant number of premenopausal women with MBC. The unavailability of effective therapies has measurable consequences. Progress in this area demands a concerted effort to prevent further loss of lives.

Identification of High-Affinity Inhibitors of Cyclin-Dependent Kinase 2 Towards Anticancer Therapy

Cyclin-dependent kinase 2 (CDK2) is an essential protein kinase involved in the cell cycle regulation. The abnormal activity of CDK2 is associated with cancer progression and metastasis. Here, we have performed structure-based virtual screening of the PubChem database to identify potent CDK2 inhibitors. First, we retrieved all compounds from the PubChem database having at least 90% structural similarity with the known CDK2 inhibitors. The selected compounds were subjected to structure-based molecular docking studies to investigate their pattern of interaction and estimate their binding affinities with CDK2. Selected compounds were further filtered out based on their physicochemical and ADMET properties. Detailed interaction analysis revealed that selected compounds interact with the functionally important residues of the active site pocket of CDK2. All-atom molecular dynamics simulation was performed to evaluate conformational changes, stability and the interaction mechanism of CDK2 in-complex with the selected compound. We found that binding of 6-N,6-N-dimethyl-9-(2-phenylethyl)purine-2,6-diamine stabilizes the structure of CDK2 and causes minimal conformational change. Finally, we suggest that the compound (PubChem ID 101874157) would be a promising scaffold to be further exploited as a potential inhibitor of CDK2 for therapeutic management of cancer after required validation.

Targeting Cyclin-Dependent Kinases for Treatment of Gynecologic Cancers

Ovarian, uterine/endometrial, and cervical cancers are major gynecologic malignancies estimated to cause nearly 30,000 deaths in 2018 in US. Defective cell cycle regulation is the hallmark of cancers underpinning the development and progression of the disease. Normal cell cycle is driven by the coordinated and sequential rise and fall of cyclin-dependent kinases (CDK) activity. The transition of cell cycle phases is governed by the respective checkpoints that prevent the entry into the next phase until cellular or genetic defects are repaired. Checkpoint activation is achieved by p53- and ATM/ATR-mediated inactivation of CDKs in response to DNA damage. Therefore, an aberrant increase in CDK activity and/or defects in checkpoint activation lead to unrestricted cell cycle phase transition and uncontrolled proliferation that give rise to cancers and perpetuate malignant progression. Given that CDK activity is also required for homologous recombination (HR) repair, pharmacological inhibition of CDKs can be exploited as a synthetic lethal approach to augment the therapeutic efficacy of PARP inhibitors and other DNA damaging modalities for the treatment of gynecologic cancers. Here, we overview the basic of cell cycle and discuss the mechanistic studies that establish the intimate link between CDKs and HR repair. In addition, we present the perspective of preclinical and clinical development in small molecule inhibitors of CDKs and CDK-associated protein targets, as well as their potential use in combination with hormonal therapy, PARP inhibitors, chemotherapy, and radiation to improve treatment outcomes.