Cyclin dependent kinase 4/6 inhibitor palbociclib synergizes with BCL2 inhibitor venetoclax in experimental models of mantle cell lymphoma without RB1 deletion.

BACKGROUND: Mantle cell lymphoma (MCL) is a chronically relapsing malignancy with deregulated cell cycle progression. We analyzed efficacy, mode of action, and predictive markers of susceptibility to palbociclib, an approved CDK 4/6 inhibitor, and its combination with venetoclax, a BCL2 inhibitor. METHODS: A panel of nine MCL cell lines were used for in vitro experiments. Four patient derived xenografts (PDX) obtained from patients with chemotherapy and ibrutinib-refractory MCL were used for in vivo proof-of-concept studies. Changes of the mitochondrial membrane potential, energy-metabolic pathways, AKT activity, and pro-apoptotic priming of MCL cells were evaluated by JC-1 staining, Seahorse XF analyser, genetically encoded fluorescent AKT reporter, and BH3 profiling, respectively. MCL clones with gene knockout or transgenic (over)expression of CDKN2A, MYC, CDK4, and RB1 were used to estimate impact of these aberrations on sensitivity to palbociclib, and venetoclax. RESULTS: Co-targeting MCL cells with palbociclib and venetoclax induced cytotoxic synergy in vitro and in vivo. Molecular mechanisms responsible for the observed synthetic lethality comprised palbociclib-mediated downregulation of anti-apoptotic MCL1, increased levels of proapoptotic BIM bound on both BCL2, and BCL-XL and increased pro-apoptotic priming of MCL cells mediated by BCL2-independent mechanisms, predominantly palbociclib-triggered metabolic and mitochondrial stress. Loss of RB1 resulted in palbociclib resistance, while deletion of CDKN2A or overexpression of CDK4, and MYC genes did not change sensitivity to palbociclib. CONCLUSIONS: Our data strongly support investigation of the chemotherapy-free palbociclib and venetoclax combination as an innovative treatment strategy for post-ibrutinib MCL patients without RB1 deletion.

The Unveiling of Therapeutic Targets for Alzheimer's Disease: An Integrative Review.

Alzheimer's disease (AD) is characterized by a complex pathological landscape, necessitating a comprehensive treatment approach. This concise review paper delves into the idea of addressing multiple mechanisms in AD, summarizing the latest research findings on pathogenesis, risk factors, diagnostics, and therapeutic strategies. The etiology of AD is multifaceted, involving genetic, environmental, and lifestyle factors. The primary feature is the accumulation of amyloid-- beta and tau proteins, leading to neuroinflammation, synaptic dysfunction, oxidative stress, and neuronal loss. Conventional single-target therapies have shown limited effectiveness, prompting a shift toward simultaneously addressing multiple disease-related processes. Recent advancements in AD research underscore the potential of multifaceted therapies. This review explores strategies targeting both tau aggregation and amyloid-beta, along with interventions to alleviate neuroinflammation, enhance synaptic function, and reduce oxidative stress. In conclusion, the review emphasizes the growing importance of addressing various pathways in AD treatment. A holistic approach that targets different aspects of the disease holds promise for developing effective treatments and improving the quality of life for Alzheimer's patients and their caregivers.

Acute-on-Chronic Liver Failure Incited by Cyclin-Dependent Kinase Inhibitor Therapy for Breast Cancer Effectively Treated With Liver Transplantation.

Cyclin-dependent kinase 4/6 inhibitors are targeted therapies demonstrated to significantly improve overall survival as adjuvant treatment of estrogen receptor-positive breast cancers. Although intended to preferentially arrest cell cycle transitions in tumor cells, these agents can have undesirable systemic side effects, including hepatotoxicity. We report the first case of cyclin-dependent kinase 4/6 inhibitor therapy leading to acute-on-chronic liver failure requiring liver transplantation. Our case highlights the multidisciplinary approach required to manage acute-on-chronic liver failure induced by cancer-directed therapies in those with extrahepatic malignancies.

Polypharmacy and drug-drug interactions in metastatic breast cancer patients receiving cyclin-dependent kinase (CDK) 4/6 inhibitors.

INTRODUCTION: Cyclin-dependent kinase (CDK) 4/6 inhibitors have significantly changed the treatment strategy for patients with locally advanced or metastatic hormone receptor positive (HR+), human epidermal growth factor 2 negative (HER2) breast cancer. The purpose of the study was to determine the prevalence of drug-drug interactions (DDI) in breast cancer patients using CDK 4/6 inhibitors and the extent of DDI reflected in the clinic and to increase clinical awareness among physicians. METHOD: The data of 115 metastatic breast cancer patients using CDK 4/6 inhibitors who were admitted to the Medical Oncology outpatient clinic between July 2021 and July 2023 were retrospectively reviewed. The Drugs.com® Drug Interaction Checker application was used for the interaction between the CDK 4/6 inhibitor and other drugs. RESULTS: Among patients included in the study, 97.3% had at least one additional drug use. We have identified a total of 170 potential DDI risks in 63.5 % of patients. Among these, 50.5% had a major potential DDI. In our study, there was a potential risk of QT prolongation in 45.2% of 170 DDI, an increase in the potential toxicity of the additional drug in 44.1%, an increase in the potential toxicity of the CDK 4/6 inhibitor in 5.3%, a decrease in the potential efficacy of the CDK 4/6 inhibitor in 2.9%, a decrease in the potential efficacy of the additional drug in 1.1%, and a serious potential infection risk in 1.1%. Most of the drug interactions were QT prolongation and increased toxicity of the additional drug. In terms of cardiovascular events, grade-2 and grade-3 QTc prolongation was found in 4.3% and 1.7% of these interactions, respectively. When evaluated in terms of CDK 4/6 inhibitor subtype, there was a potential risk of DDI at major level with Ribocilib and at moderate level with Palbociclib. CONCLUSION: If CDK 4/6 inhibitors interact with concomitant drugs, they may cause an increase in the incidence of cardiac side effects and a decrease in the effect of the CDK 4/6 inhibitor or additional drug or an increase in toxicity. Increasing awareness of this issue will help to reduce the rates of side effects or toxicity and provide effective antitumour therapy.

G1 Dynamics at the Crossroads of Pluripotency and Cancer.

G1 cell cycle phase dynamics are regulated by intricate networks involving cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors, which control G1 progression and ensure proper cell cycle transitions. Moreover, adequate origin licensing in G1 phase, the first committed step of DNA replication in the subsequent S phase, is essential to maintain genome integrity. In this review, we highlight the intriguing parallels and disparities in G1 dynamics between stem cells and cancer cells, focusing on their regulatory mechanisms and functional outcomes. Notably, SOX2, OCT4, KLF4, and the pluripotency reprogramming facilitator c-MYC, known for their role in establishing and maintaining stem cell pluripotency, are also aberrantly expressed in certain cancer cells. In this review, we discuss recent advances in understanding the regulatory role of these pluripotency factors in G1 dynamics in the context of stem cells and cancer cells, which may offer new insights into the interconnections between pluripotency and tumorigenesis.

Cytomegalovirus cyclin-dependent kinase ortholog vCDK/pUL97 undergoes regulatory interaction with human cyclin H and CDK7 to codetermine viral replication efficiency.

Human cytomegalovirus (HCMV) infection is shaped by a tightly regulated interplay between viral and cellular proteins. Distinct kinase activities, such as the viral cyclin-dependent kinase ortholog (vCDK) pUL97 and cellular CDK7 are both crucial for efficient viral replication. Previously, we reported that both kinases, vCDK/pUL97 and CDK7, interact with cyclin H, thereby achieving an enhanced level of kinase activity and overall functionality in viral replication. Here we provide a variety of novel results, as generated on a methodologically extended basis, and present a concept for the codetermination of viral replication efficiency through these kinase activities: (i) cyclin H expression, in various human cell types, is substantially upregulated by strains of HCMV including the clinically relevant HCMV Merlin; (ii) vCDK/pUL97 interacts with human cyclin H in both HCMV-infected and plasmid-transfected cell systems; (iii) a doxycycline-inducible shRNA-dependent knock-down (KD) of cyclin H significantly reduces pUL97 activity (qSox in vitro kinase assay); (iv) accordingly, pUL97 in vitro kinase activity is seen significantly increased upon addition of recombinant cyclin H; (v) as a point of specific importance, human CDK7 activity shows an increase by vCDK/pUL97-mediated trans-stimulation (whereas pUL97 is not stimulated by CDK7); (vi) phosphosite-specific antibodies indicate an upregulated CDK7 phosphorylation upon HCMV infection, as mediated through a pUL97-specific modulatory effect (i.e. shown by pUL97 inhibitor treatment or pUL97-deficient viral mutant); (vii) finally, an efficient KD of cyclin H in primary fibroblasts generally results in an impaired HCMV replication efficiency as measured on protein and genomic levels. These results show evidence for the codetermination of viral replication by vCDK/pUL97, cyclin H and CDK7, thus supporting the specific importance of cyclin H as a central regulatory factor, and suggesting novel targeting options for antiviral drugs.

Faecal microbiota composition is related to response to CDK4/6-inhibitors in metastatic breast cancer: A prospective cross-sectional exploratory study.

BACKGROUND: Cyclin-dependent kinase (CDK)4/6-inhibitors with endocrine therapy represent the standard of treatment of hormone receptor-positive(HR+)/human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC). Gut microbiota seems to predict treatment response in several tumour types, being directly implied in chemotherapy resistance and development of adverse effects. No evidence is available on gut microbiota impact on efficacy of HR+ breast cancer treatment. PATIENTS AND METHODS: We assessed the potential association among faecal microbiota and therapeutic efficacy of CDK4/6-inhibitors on 14 MBC patients classified as responders (R) and non-responders (NR) according to progression-free survival. A stool sample was collected at baseline and V3-V4 16S targeted sequencing was employed to assess its bacterial composition. Statistical associations with R and NR were studied. RESULTS: No significant differences were observed between R and NR in terms of α-/ß-diversity at the phylum and species level. Machine-learning (ML) algorithms evidenced four bacterial species as a discriminant for R (Bifidobacterium longum, Ruminococcus callidus) and NR (Clostridium innocuum, Schaalia odontolytica), and an area under curve (AUC) of 0.946 after Random Forest modelling. Network analysis evidenced two major clusters of bacterial species, named Species Interacting Groups (SIG)1-2, with SIG1 harbouring 75% of NR-related bacterial species, and SIG2 regrouping 76% of R-related species (p < 0.001). Cross-correlations among several patients' circulating immune cells or biomarkers and bacterial species' relative abundances showed associations with potential prognostic implications. CONCLUSIONS: Our results provide initial insights into the gut microbiota involvement in sensitivity and/or resistance to CDK4/6-inhibitors + endocrine therapy in MBC. If confirmed in larger trials, several microbiota manipulation strategies might be hypothesised to improve response to CDK4/6-inhibitors.

[Advances of the regulatory mechanism of cyclin, cyclin- dependent kinases and related kinase inhibitors in cell cycle progression].

Cell cycle plays a crucial role in cell development. Cell cycle progression is mainly regulated by cyclin dependent kinase (CDK), cyclin and endogenous CDK inhibitor (CKI). Among these, CDK is the main cell cycle regulator, binding to cyclin to form the cyclin-CDK complex, which phosphorylates hundreds of substrates and regulates interphase and mitotic progression. Abnormal activity of various cell cycle proteins can cause uncontrolled proliferation of cancer cells, which leads to cancer development. Therefore, understanding the changes in CDK activity, cyclin-CDK assembly and the role of CDK inhibitors will help to understand the underlying regulatory processes in cell cycle progression, as well as provide a basis for the treatment of cancer and disease and the development of CDK inhibitor-based therapeutic agents. This review focuses on the key events of CDK activation or inactivation, and summarizes the regulatory processes of cyclin-CDK at specific times and locations, as well as the progress of research on relevant CDK inhibitor therapeutics in cancer and disease. The review concludes with a brief description of the current challenges of the cell cycle process, with the aim to provide scientific references and new ideas for further research on cell cycle process.

Regulation of Ferroptosis by Transcription Factor E2F1 and RB.

Tumor suppressor RB binds to E2F family proteins and modulates cell cycle progression. Cyclin dependent kinases (CDK) regulate the interaction of RB/E2F by phosphorylating RB. Previously, we have revealed that CDK2, RB and E2F inhibit ferroptosis. Ferroptosis is a non-apoptotic, iron-dependent form of cell death characterized by toxic lipid peroxidation. Here we provide evidence that CDK2 suppresses ferroptosis through phosphorylation of RB. We approach this question by overexpressing WT-RB or a mutant RB that cannot be phosphorylated by CDKs (RBΔCDK) along with CDK2/cyclinE followed by analysis of ferroptosis. We also observed that E2F1 regulates of both pro and anti-ferroptotic proteins including ALOX5, MYC SLC7A11, ATF4, and GPX4 and finally renders a net inhibitory role in ferroptosis. Interestingly, we also found a cell type dependent compensatory effect of E2F3 upon E2F1 depletion. This compensatory effect resulted in no change of ferroptotic target genes after E2F1 knock down in an osteosarcoma cell line. Taken together, our study reveals that cancer cells protect themselves from ferroptosis through cell cycle regulatory proteins.

Advances of the regulatory mechanism of cyclin, cyclin- dependent kinases and related kinase inhibitors in cell cycle progression / 生物工程学报

Cell cycle plays a crucial role in cell development. Cell cycle progression is mainly regulated by cyclin dependent kinase (CDK), cyclin and endogenous CDK inhibitor (CKI). Among these, CDK is the main cell cycle regulator, binding to cyclin to form the cyclin-CDK complex, which phosphorylates hundreds of substrates and regulates interphase and mitotic progression. Abnormal activity of various cell cycle proteins can cause uncontrolled proliferation of cancer cells, which leads to cancer development. Therefore, understanding the changes in CDK activity, cyclin-CDK assembly and the role of CDK inhibitors will help to understand the underlying regulatory processes in cell cycle progression, as well as provide a basis for the treatment of cancer and disease and the development of CDK inhibitor-based therapeutic agents. This review focuses on the key events of CDK activation or inactivation, and summarizes the regulatory processes of cyclin-CDK at specific times and locations, as well as the progress of research on relevant CDK inhibitor therapeutics in cancer and disease. The review concludes with a brief description of the current challenges of the cell cycle process, with the aim to provide scientific references and new ideas for further research on cell cycle process.

Nuclear-cytoplasmic compartmentalization of cyclin B1-Cdk1 promotes robust timing of mitotic events.

The cyclin-dependent kinase (Cdk1) oscillator is widely characterized in homogenized cytosolic extracts, leaving unclear the impact of nucleocytoplasmic compartmentalization. Here, by developing a Förster resonance energy transfer (FRET) biosensor, we track Cdk1 spatiotemporal dynamics in reconstituted cells with or without side by side and find compartmentalization significantly modulates clock properties previously found in bulk studies. Although nucleus-absent cells display highly tunable frequency, the nucleus-present cells maintain constant frequency against cyclin B1 variations. Despite high expression variability, cyclin degraded within the same duration, enabling a robust mitotic phase. Moreover, Cdk1 and cyclin B1 cycle rigorously out-of-phase, ensuring wide phase-plane orbits, essential for oscillation robustness. Although Cdk1 in homogeneous extracts is well known for delayed switch-like activation, we find active cyclin B1-Cdk1 accumulates in nuclei, without delay, until the nuclear envelope breakdown (NEB) when another abrupt activation triggers anaphase. Cdk1 biphasic activation and spatial compartmentalization may together coordinate the accurate ordering of different downstream events.

The Cyclin-Dependent Kinase 4/6 Inhibitor Abemaciclib Is Tolerated Better than Palbociclib by Advanced Breast Cancer Patients with High Serum Albumin Levels.

The cyclin-dependent kinase (CDK) 4/6 inhibitors, palbociclib and abemaciclib, have been approved in Japan. However, the selection criteria for these drugs have not been established. Hence, we aimed to identify the risk factors for CDK4/6 inhibitor-induced intolerable adverse events requiring dose reduction or therapy cessation and to establish useful markers for choosing the appropriate CDK4/6 inhibitor, based on the incidence of the intolerable adverse events. This retrospective cohort analysis included patients with advanced breast cancer who received 125 mg/d palbociclib or 300 mg/d abemaciclib. We defined significant adverse events (SAEs) as side effects requiring dose reduction or therapy cessation. Thirty-six percent of the patients who received palbociclib (9/25) and 27.3% of those who received abemaciclib (9/33) experienced SAEs. In palbociclib and abemaciclib groups, baseline white blood cell (WBC) counts and serum albumin (ALB) levels, respectively, were significantly lower in patients who experienced SAEs than in those who did not (palbociclib: p = 0.007; abemaciclib: p = 0.004). According to the receiver operating characteristic curve analysis, the optimal cutoff values for baseline WBC count and ALB level were 5700/µL and 4.0 g/dL, respectively. Among patients with ALB levels >4.0 g/dL, the incidence of abemaciclib-induced SAEs was significantly lower than that of the palbociclib-induced SAEs (1/17 (5.9%) vs. 6/14 (42.9%), odds ratio: 11.0, 95% confidence interval: 1.07-583, p = 0.0281). Thus, a baseline WBC count ≤5700/µL and ALB level ≤4.0 g/dL may be risk factors for palbociclib and abemaciclib-induced SAEs, respectively. Also, high ALB levels can serve as a useful marker for choosing abemaciclib.

Infectious complications of cyclin-dependent kinases 4 and 6 inhibitors in patients with hormone-receptor-positive metastatic breast cancer: a systematic review and meta-analysis.

AIM: The combination of cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors plus endocrine therapy (ET) improved the survival outcomes and became the standard of care in the treatment of metastatic hormone-positive breast cancer. However, these combinations increased the risk of neutropenia compared with ET alone. While the infection-related mortalities did not seem to be increased, the exact risk of infections with CDK 4/6 inhibitor and ET combinations is relatively understudied. Therefore, we performed a meta-analysis of CDK 4/6 inhibitor clinical trials to assess the infection risk of adding CDK4/6 inhibitors to ET. MATERIAL AND METHOD: We systemically searched the PubMed database for relevant clinical trials. For each study, all grade and grade 3 or higher infections, upper respiratory tract infections (URTI), urinary tract infections (UTI), pneumonia, and febrile neutropenia rates were recorded whenever available. The hazard ratios (HR) with a 95% confidence interval (CI) of infection risk were calculated via the generic inverse-variance method with a random-effects model. RESULTS: Nine eligible studies were included in the analyses (MONALEESA-2,3,7, MONARCH-2,3, MONARCH plus, PALOMA-1,2,3). In the meta-analysis of these studies, CDK 4/6 inhibitors plus ET arms were associated with increased all grade infections (HR 1.77, 95% CI 1.56-2.01, p < 0.00001), grade 3 or higher infections, (HR 1.77, 95% CI 1.28-2.43, p = 0.0005), UTIs (HR 1.59, 95% CI 1.19-2.12, p = 0.002), and febrile neutropenia (HR 4.28, 95% CI 1.73-10.62, p = 0.002). CONCLUSION: In this meta-analysis, we observed that adding CDK4/6 inhibitors to ET significantly increased the risk of all grade, grade 3 or higher infections, and urinary tract infections. We propose that closer follow-up for infections should be considered for metastatic breast cancer patients using CDK 4/6 inhibitors. This may help clinicians to recognize infections earlier which prevents early death from infection.

A look at current and potential treatment approaches for hormone receptor-positive, HER2-negative early breast cancer.

The heterogeneity of hormone receptor (HR)-positive, HER2-negative early breast cancers reinforces the importance of individualized, risk-adapted treatment approaches. Numerous factors contribute to the risk for recurrence, including clinical tumor features, individual biomarkers, and genomic risk. Current standard approaches for patients with HR-positive, HER2-negative, early stage disease focus on endocrine therapy and chemotherapy. The specific treatment regimen and duration of adjuvant therapy should be selected based on accurate risk assessment, tolerability of available therapies, and consideration for patient preferences. For patients with high-risk features, such as highly proliferative tumors, large tumor size, and significant nodal involvement, the risk for recurrence remains clinically significant despite appropriate adjuvant treatment with current standards of care. This has driven investigation into novel treatment approaches, including the addition of cyclin-dependent kinase 4 and 6 inhibitors to adjuvant endocrine therapy. Cyclin-dependent kinase 4 and 6 inhibition has demonstrated significant efficacy in patients with high-risk, HR-positive, HER2-negative, nonmetastatic breast cancer and now offers a new strategy to greatly improve outcomes in this difficult to treat patient population.; LAY SUMMARY: Hormone receptor (HR)-positive, HER2-negative early breast cancers are highly diverse and need to be managed differently for individual patients. The use of adjuvant endocrine therapy and chemotherapy should be driven by a patient's risk for recurrence, preferences, and risk for side effects. Patients with high-risk tumors have a persistently elevated risk for recurrence despite current standards of care. Emerging cyclin-dependent kinase 4 and 6 inhibitors are highly effective when added to endocrine therapy in high-risk, HR-positive early breast cancer and have the potential to improve patient outcomes in this difficult to treat patient population.

PIP5K1α is Required for Promoting Tumor Progression in Castration-Resistant Prostate Cancer.

PIP5K1α has emerged as a promising drug target for the treatment of castration-resistant prostate cancer (CRPC), as it acts upstream of the PI3K/AKT signaling pathway to promote prostate cancer (PCa) growth, survival and invasion. However, little is known of the molecular actions of PIP5K1α in this process. Here, we show that siRNA-mediated knockdown of PIP5K1α and blockade of PIP5K1α action using its small molecule inhibitor ISA-2011B suppress growth and invasion of CRPC cells. We demonstrate that targeted deletion of the N-terminal domain of PIP5K1α in CRPC cells results in reduced growth and migratory ability of cancer cells. Further, the xenograft tumors lacking the N-terminal domain of PIP5K1α exhibited reduced tumor growth and aggressiveness in xenograft mice as compared to that of controls. The N-terminal domain of PIP5K1α is required for regulation of mRNA expression and protein stability of PIP5K1α. This suggests that the expression and oncogenic activity of PIP5K1α are in part dependent on its N-terminal domain. We further show that PIP5K1α acts as an upstream regulator of the androgen receptor (AR) and AR target genes including CDK1 and MMP9 that are key factors promoting growth, survival and invasion of PCa cells. ISA-2011B exhibited a significant inhibitory effect on AR target genes including CDK1 and MMP9 in CRPC cells with wild-type PIP5K1α and in CRPC cells lacking the N-terminal domain of PIP5K1α. These results indicate that the growth of PIP5K1α-dependent tumors is in part dependent on the integrity of the N-terminal sequence of this kinase. Our study identifies a novel functional mechanism involving PIP5K1α, confirming that PIP5K1α is an intriguing target for cancer treatment, especially for treatment of CRPC.

Cyclin-Dependent Kinase Synthetic Lethality Partners in DNA Damage Response.

Cyclin-dependent kinases (CDKs) are pivotal mediators and effectors of the DNA damage response (DDR) that regulate both the pathway components and proteins involved in repair processes. Synthetic lethality (SL) describes a situation in which two genes are linked in such a way that the lack of functioning of just one maintains cell viability, while depletion of both triggers cell death. Synthetic lethal interactions involving CDKs are now emerging, and this can be used to selectively target tumor cells with DNA repair defects. In this review, SL interactions of CDKs with protooncogene products MYC, poly (ADP-ribose) polymerase (PARP-1), and cellular tumor antigen p53 (TP53) are discussed. The individual roles of each of the SL partners in DDR are described.

Cyclin-dependent kinases in DNA damage response.

The cyclin-dependent kinase (CDK) family plays a critical role in a variety of signaling pathways that regulate transcription and cell-cycle progression. Recently, the role of CDKs in DNA damage response (DDR) has emerged. CDKs affect both damage signaling and DNA repair, contributing to the fidelity of the cell division process as well as the maintenance of genomic integrity following DNA damage. This is due to the modulatory role of CDKs on double-strand break repair (DSBR) components, including their influence on enzymes involved in homologous recombination (HR) and non-homologous end-joining (NHEJ). In this review, the impact of CDKs on DDR and DNA repair is discussed.

Cyclin-Dependent Kinases (CDKs) and the Human Cytomegalovirus-Encoded CDK Ortholog pUL97 Represent Highly Attractive Targets for Synergistic Drug Combinations.

Human cytomegalovirus (HCMV) is a pathogenic human herpesvirus associated with serious, potentially life-threatening symptoms in the immunocompromised or immunonaïve host. The limitations encountered by antiviral therapy options currently available include a narrow panel of accessible targets, the induction of viral drug resistance as well as severe drug dosage-mediated side-effects. Improved drug-targeting strategies to resolve these issues are the focus of our investigations. In particular, pharmaceutical kinase inhibitors (PKIs), either directed to host kinases or directed to the viral protein kinase pUL97, have been considered to overcome these restrictions. Recently, we reported the identification of a synergistic combination of two PKIs directed to host cyclin-dependent kinase 7 (CDK7) and viral CDK ortholog pUL97. Here, we substantiate these findings with the following results: (i) true drug synergy was exhibited by various chemical classes of PKI pairs directed to pUL97 and CDK7; (ii) no putative amplification of cytotoxicity by these drug combinations was observed; (iii) a reduction in drug dosage levels for synergistic combinations was defined on a quantitative basis and compared to monotreatments; (iv) the quantities of target proteins CDK7 and pUL97 expressed in HCMV-infected cells were assessed by confocal imaging, indicating a strong down-modulation of CDK7 levels as a result of synergistic drug treatment; (v) the functional importance of these target kinases, both binding to cyclin H, was illustrated by assessing HCMV replication under the viral genomic deletion of ORF-UL97 or cellular cyclin knock-out; (vi) new combinations of HCMV-specific drug synergy were demonstrated for solely host-directed treatments using PKIs against CDK2, CDK7, CDK8 and/or CDK9 and (vii) a triple PKI combination provided further support for the synergy approach. With these combined findings, this study highlights the potential of therapeutic drug combinations of approved, developmental and preclinical PKIs for expanding future options for anti-HCMV therapy.

Interstitial lung disease in patients treated with Cyclin-Dependent Kinase 4/6 inhibitors: A systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Cyclin-Dependent Kinase (CDK) 4/6 inhibitors have shown significant clinical activity in cancer patients. However, some concerns regarding rare adverse events (AEs) have occurred including interstitial lung disease (ILD)/pneumonitis, for which data are deficient. The aim of this study was to evaluate the overall incidence and risk of ILD/pneumonitis related to CDK4/6 inhibitors in randomized controlled trials (RCTs). METHODS: Electronic databases and ClinicalTrials.gov were searched from inception to October 1, 2021 for RCTs reporting the occurrence of LD/pneumonitis in cancer patients treated with CDK4/6 inhibitors. Peto odds ratios (Peto ORs) and 95% confidence intervals (CIs) were used to pool the study. RESULTS: 12 RCTs with a total of 16,060 patients were eligible. The overall incidence of all-grade ILD/pneumonitis was 1.6% (131/8407) in the treatment group compared with 0.7% (50/7349) in the control group. CDK4/6 inhibitors significantly increased the risk of all-grade ILD/pneumonitis with a pooled Peto OR of 2.12 (95% CI [1.57, 2.86], P < 0.00001) with no heterogeneity (I2 = 0%, χ2 P = 0.98). A higher incidence of grade 3 or higher ILD/pneumonitis was also observed in the treatment group (0.2%, 16/7087) compared with the control group (0.05%, 3/6617) with a Peto OR of 3.22 (95% CI [1.28, 8.09], P = 0.01) with no heterogeneity (I2 = 0%, χ2 P = 0.62). Two grade 5 pneumonitis were reported in the included studies. Subgroup analyses did not show any significant difference. CONCLUSIONS: The risk of all-grade and grade 3 or higher ILD/pneumonitis was higher in patients treated with CDK4/6 inhibitors compared to controls. The awareness for these rare AEs in the application of CDK4/6 inhibitors should be enhanced. Further studies are required to validate the mechanisms and the risk factors of ILD/pneumonitis with CDK4/6 inhibitors.