Myelopreservation with Trilaciclib in Patients Receiving Topotecan for Small Cell Lung Cancer: Results from a Randomized, Double-Blind, Placebo-Controlled Phase II Study

Clinical Activity and Safety of Anlotinib Combined with PD-1 Blockades for Patients with Previously Treated Small Cell Lung Cancer

Objective

Anlotinib was the standard monotherapy for patients with previously treated small cell lung cancer (SCLC) in recent years. Programmed cell death protein 1 (PD-1) blockade combined with antiangiogenic targeted drugs have proved to play a synergistic action for cancer treatment clinically. Consequently, the present study was to investigate the efficacy and safety of anlotinib combined with PD-1 blockades for patients with previously treated SCLC.

Methods

A total of 36 patients with SCLC who were treated with at least one previous systemic chemotherapy regimen participated in this study retrospectively. All the patients were administered with anlotinib plus PD-1 blockades therapy. Clinical activity was assessed according to the change of target lesion by imaging evidence and all the subjects were followed up regularly. Safety profiles were collected and documented during the treatment. Univariate analysis was carried out using Log rank test and multivariate analysis was adjusted by Cox regression analysis.

Results

All the 36 patients with previously treated SCLC were able to have their efficacy and safety profile evaluated. The best overall response of the combination regimen showed that complete response was observed in one patient, partial response was noted in 9 patients, stable disease was reported in 19 patients, progressive disease was seen in 7 patients. Therefore, the objective response rate (ORR) of the 36 patients was 27.8% (95% CI: 14.2-45.2%), disease control rate (DCR) was 80.6% (95% CI: 64.0-91.8%). Regarding the prognostic data, the median PFS and OS of the 36 patients was 4.6 months (95% CI: 3.13-6.07) and 9.3 months (95% CI: 3.30-15.30), respectively. The most common treatment-related adverse reactions were hypertension (52.8%), fatigue (47.2%), diarrhea (38.9%), hand and foot reaction (38.9%) and dermal toxicity (33.3%). Furthermore, multivariate Cox regression analysis for PFS indicated that ECOG performance status was an independent factor to predict PFS.

Conclusion

Anlotinib combined with PD-1 blockades regimen preliminarily demonstrated encouraging efficacy and tolerable safety for patients with previously treated SCLC. The conclusion should be validated in prospective clinical trials subsequently.

Thrombotic events in patients using cyclin dependent kinase 4/6 inhibitors, analysis of existing ambulatory risk assessment models and the potential influences of tumor specific risk factors

Cyclin dependent kinase 4 of 6 inhibitors (CDKi) are key therapeutics in the treatment of advanced breast cancer and have recently been approved in small cell lung cancer for the prevention of myelosuppression. Thrombotic events have emerged as a significant treatment related adverse event in up to 5% of patients in clinical trials and has been reported at higher rates, up to 10%, in real world analysis. The prothrombotic mechanisms of CDKis, however, remain unknown. Cancer specific risk assessment models exist to identify who may be at highest risk of thrombosis and who could potentially benefit from prophylactic anticoagulation. However, these models may not be accurate in patients taking CDKis and may not fully capture recently identified thrombotic risk factors such as tumor specific somatic mutations. In the following manuscript, we summarize the literature on thrombotic events with CDKis in clinical trials and real-world settings, review the existing thrombosis risk assessment models for ambulatory cancer patients, and discuss the literature on tumor mutations and role in cancer associated thrombosis.

Real-world burden of chemotherapy-induced myelosuppression in patients with small cell lung cancer: a retrospective analysis of electronic medical data from community cancer care providers

AIMS

Chemotherapy-induced myelosuppression, which commonly exhibits as neutropenia, anemia, or thrombocytopenia, represents a substantial burden for patients with cancer that affects health-related quality of life and increases healthcare resource utilization (HCRU). We evaluated the burden of myelosuppression among chemotherapy-treated patients with small cell lung cancer (SCLC) using real-world data from community cancer care providers in the Western United States.

MATERIALS AND METHODS

This was a retrospective, observational analysis of electronic medical records (EMRs) from Providence St. Joseph Health hospital-associated oncology clinics between January 2016 and December 2019. Patient demographics were assessed from the date of first SCLC diagnosis in adult patients with chemotherapy-induced grade ≥3 myelosuppression in first-line (1L) or second-line-and-beyond (2L+) treatment settings. Myelosuppressive adverse events (AEs), treatment patterns, and HCRU were assessed from the date of chemotherapy initiation (index date) until 12 months, date of the last visit, date of death, or study end, whichever occurred earliest.

RESULTS

Of 347 eligible patients with SCLC who had received chemotherapy (mean age 66; 49% female), all had received at least 1L treatment, and 103 (29.7%) had a 2L + treatment recorded within the EMR during the study period. Of 338 evaluable patients with longitudinal laboratory data, 206 (60.9%) experienced grade ≥3 myelosuppressive AEs, most commonly neutropenia, anemia, and thrombocytopenia (44.9, 41.1, and 25.4 per 100 patients, respectively). Rates of granulocyte colony-stimulating factor use and red blood cell transfusions were 47.0 and 41.7 per 100 patients, respectively. There was a trend toward increasing the use of supportive care interventions and visits to inpatient and outpatient facilities in patients with myelosuppressive AEs in more than one cell lineage.

CONCLUSIONS

Chemotherapy-induced myelosuppression places a substantial real-world burden on patients with SCLC in the community cancer care setting. Innovations to protect bone marrow from chemotherapy-induced damage have the potential to reduce this burden.

Small Cell Lung Cancer, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Small Cell Lung Cancer (SCLC) provide recommended management for patients with SCLC, including diagnosis, primary treatment, surveillance for relapse, and subsequent treatment. This selection for the journal focuses on metastatic (known as extensive-stage) SCLC, which is more common than limited-stage SCLC. Systemic therapy alone can palliate symptoms and prolong survival in most patients with extensive-stage disease. Smoking cessation counseling and intervention should be strongly promoted in patients with SCLC and other high-grade neuroendocrine carcinomas. The "Summary of the Guidelines Updates" section in the SCLC algorithm outlines the most recent revisions for the 2022 update, which are described in greater detail in this revised Discussion text.

Trilaciclib and the economic value of multilineage myeloprotection from chemotherapy-induced myelosuppression among patients with extensive-stage small cell lung cancer treated with first-line chemotherapy

AIMS

Proliferating hematopoietic stem and progenitor cells (HSPCs) are susceptible to chemotherapy-induced damage, resulting in myelosuppressive adverse events (AEs) such as neutropenia, anemia, and thrombocytopenia that are associated with high health care costs and decreased quality of life (QoL). In this study, a trial-based cost-effectiveness analysis was performed to help assess the economic impact of administering trilaciclib, a myeloprotective therapy that protects multilineage HSPCs from chemotherapy-induced damage, prior to standard first-line chemotherapy, using data from a pivotal Phase II study of trilaciclib in the setting of extensive-stage small cell lung cancer (ES-SCLC, NCT03041311).

METHOD

The aim of this study was to assess the cost-effectiveness of administering trilaciclib prior to chemotherapy versus chemotherapy alone among patients with ES-SCLC from a United States payer perspective. Data on the rate and frequency of myelosuppressive AEs and health utility were derived from the pivotal study of trilaciclib. Costs of managing myelosuppressive AEs and costs of chemotherapy treatment were sourced from published literature. Outcomes included the number of myelosuppressive AEs, costs (in 2021 US dollars), quality-adjusted life-years (QALYs), incremental cost, incremental QALY, and an incremental cost-effectiveness ratio.

RESULTS

Administering trilaciclib prior to chemotherapy was associated with a reduction in neutropenia (82%), febrile neutropenia (75%), anemia (43%), and thrombocytopenia (96%) compared with chemotherapy alone. Additionally, trilaciclib prior to chemotherapy was cost-saving compared with chemotherapy alone ($99,919 vs $118,759, respectively) and associated with QALY improvement (0.150 vs 0.145, respectively). Probabilistic sensitivity analyses showed 58% of iterations projecting cost savings and QALY improvement with trilaciclib.

CONCLUSIONS

The findings suggest that the use of trilaciclib prior to first-line chemotherapy in patients with ES-SCLC can be cost-beneficial owing to fewer myelosuppressive AEs and lower costs, together with a favorable QoL profile.

Advances in Treatment of Recurrent Small Cell Lung Cancer (SCLC): Insights for Optimizing Patient Outcomes from an Expert Roundtable Discussion

Second-line treatment options for patients with relapsed, extensive-stage small cell lung cancer (ES-SCLC) are limited, and even with currently available treatments, prognosis remains poor. Until recently, topotecan (a topoisomerase I inhibitor) was the only drug approved by the United States (US) Food and Drug Administration (FDA) for the management of ES-SCLC following progression after first-line treatment with etoposide plus a platinum derivative (EP; carboplatin preferred). With the most recent approval of EP plus a programmed death ligand 1 (PD-L1) inhibitor, there are now more therapeutic options for managing ES-SCLC. A number of novel agents have emerging data for activity in relapsed ES-SCLC, and single-agent lurbinectedin (an alkylating drug and selective inhibitor of oncogenic transcription and DNA repair machinery in tumor cells) has conditional FDA approval for use in this patient population. Trilaciclib, a short-acting cyclin-dependent kinase 4/6 (CDK 4/6) inhibitor, has also been recently approved as a supportive intervention for use prior to an EP or a topotecan-containing regimen to diminish the incidence of chemotherapy-induced myelosuppression. The current review is based on a recent expert roundtable discussion and summarizes current therapeutic agents and emerging data on newer agents and biomarkers. It also provides evidence-based clinical considerations and a treatment decision tool for oncologists treating patients with relapsed ES-SCLC. This paper discusses the importance of various factors to consider when selecting a second-line treatment option, including prior first-line treatment, available second-line treatment options, tumor platinum sensitivity, and patient characteristics (such as performance status, comorbidities, and patient-expressed and perceived values).

The benefits and risks of pembrolizumab in combination with chemotherapy as first-line therapy in small-cell lung cancer: a single-arm meta-analysis of noncomparative clinical studies and randomized control trials

BACKGROUND

Although pembrolizumab has shown clinical benefit in patients with small-cell lung cancer (SCLC), its actual efficacy in combination with a conventional chemotherapy drug has not been determined. We performed this study to discern the efficacy and risk of pembrolizumab in combination with chemotherapy as first-line therapy in SCLC patients.

METHODS

We systematically searched the PubMed, ScienceDirect, Cochrane Library, Scopus, Ovid MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies. The main outcomes were overall survival (OS) and progression-free survival (PFS).

RESULTS

We identified 2980 articles and included 6 studies (5 were noncomparative open-label studies and 1 was a randomized controlled trial [RCT]) involving 396 patients in our meta-analysis. The pooled median OS (mOS) was 9.6 months (95% CI, 8.0-11.2), and the pooled median PFS (mPFS) was 4.2 months (95% CI, 2.2-6.1). The 1-year overall survival rate (OSR-1y) and 6-month progression-free survival rate (PFSR-6m) were 45.1% (95% CI, 33-57.2%) and 41.6% (95% CI, 24.3-59%), respectively. The objective response rate (ORR) was 38.8% (95% CI, 11.9-65.67%), disease control rate (DCR) was 69.30% (95% CI, 51.6-87.0%), complete response (CR) was 2.20% (95% CI, 0.8-3.7%), partial response (PR) was 34.70% (95% CI, 7.8-61.5%), and stable disease (SD) was 20.90% (95% CI, 9.1-32.6%). The grade 3-4 adverse effect (AE) rate was 20.88% (95% CI, 1.22-54.85%). The most common AEs were neutropenia (90.16%), anemia (53.21%), dysphagia (41.96%), platelet count decrease (34.87%), and esophagitis (32.89%); severe AEs included neutropenia, respiratory failure, pneumonitis, acute coronary syndrome, and colitis/intestinal ischemia.

CONCLUSIONS

The combination of pembrolizumab with conventional chemotherapy is an effective therapeutic schedule with acceptable and manageable efficacy and toxicity in patients with SCLC. More high-quality and well-designed RCTs with large sample sizes are warranted to further validate our findings.

Concerning FDA approval of trilaciclib (Cosela) in extensive-stage small-cell lung cancer

Trilaciclib is a recently approved cyclin-dependent kinase 4/6 inhibitor that is designed to decrease the incidence of chemotherapy-induced myelosuppression in adult patients with extensive-stage small-cell lung cancer receiving chemotherapy. Currently, this first-in-class therapy raises two open issues: its bio-plausibility and paucity of evidence demonstrating a lasting impact on clinical endpoints. Based on the existing phase 2 data, trilaciclib appears to be a therapy that can make a positive impact by preventing myelosuppression, but empirical validation with larger phase III trials should be conducted to confirm these benefits. The purpose of this article is to facilitate discussion about the role of trilaciclib in clinical practice and the need for additional trials.

Myeloprotective Effects of Trilaciclib Among Patients with Small Cell Lung Cancer at Increased Risk of Chemotherapy-Induced Myelosuppression: Pooled Results from Three Phase 2, Randomized, Double-Blind, Placebo-Controlled Studies

Purpose

Trilaciclib is an intravenous cyclin-dependent kinase 4/6 inhibitor indicated to decrease the incidence of chemotherapy-induced myelosuppression (CIM) by protecting hematopoietic stem and progenitor cells and immune system function from chemotherapy-induced damage (myeloprotection). Here, we investigated the myeloprotective effects of trilaciclib among patients at increased risk of CIM.

Patients and Methods

Data were pooled from three randomized, double-blind, placebo-controlled, phase 2 clinical studies of trilaciclib administered prior to chemotherapy in patients with extensive-stage small cell lung cancer (ES-SCLC). Myeloprotective outcomes were evaluated in patient subgroups based on age (<65 or ≥65 years), risk of chemotherapy-induced febrile neutropenia (FN), and risk of anemia or red blood cell (RBC) transfusions. For the FN and anemia analyses, risk factors were identified from published literature and used to classify patients into FN and anemia risk categories. Subgroup analysis based on age was also performed on patient reported outcome (PRO) measures.

Results

In total, 123 patients received trilaciclib and 119 patients received placebo. Myeloprotective benefits of trilaciclib were observed regardless of age, with greater effects observed among patients aged ≥65 years. Across FN risk factors and categories, trilaciclib had beneficial effects on neutrophil-related endpoints vs placebo, with greater effects observed in patients at higher risk of FN. Effects on RBC-related endpoints favored trilaciclib vs placebo, regardless of anemia risk factors and categories. Improvements in PROs with trilaciclib were observed irrespective of age group, but with greater improvements and less deterioration from baseline observed in older patients.

Conclusion

By both decreasing the incidence of CIM and improving quality of life, trilaciclib has the potential to allow patients receiving chemotherapy for ES-SCLC, including patients who are older or more vulnerable to CIM, to receive chemotherapy on schedule and at standard-of-care doses, and to improve the experience for patients receiving chemotherapy to treat ES-SCLC.

Clinical Trial Numbers

NCT02499770; NCT03041311; NCT02514447.

Trilaciclib prior to chemotherapy reduces the usage of supportive care interventions for chemotherapy-induced myelosuppression in patients with small cell lung cancer: Pooled analysis of three randomized phase 2 trials

Background

Supportive care interventions used to manage chemotherapy‐induced myelosuppression (CIM), including granulocyte colony‐stimulating factors (G‐CSFs), erythropoiesis‐stimulating agents (ESAs), and red blood cell (RBC) transfusions, are burdensome to patients and associated with greater costs to health care systems. We evaluated the utilization of supportive care interventions and their relationship with the myeloprotective agent, trilaciclib.

Methods

Data were pooled from three independent randomized phase 2 clinical trials of trilaciclib or placebo administered prior to chemotherapy in patients with extensive‐stage small cell lung cancer (ES‐SCLC). The impact of supportive care on the duration of severe neutropenia (DSN), occurrence of severe neutropenia (SN), and occurrence of RBC transfusions on/after week 5 was analyzed across cycles 1–4. Concordance and association between grade 3/4 anemia, RBC transfusions on/after week 5, and ESA administration was also evaluated.

Results

The use of G‐CSFs, ESAs, or RBC transfusions on/after week 5 was significantly lower among patients receiving trilaciclib versus placebo (28.5% vs. 56.3%, p < 0.0001; 3.3% vs. 11.8%, p = 0.0254; and 14.6% vs. 26.1%, p = 0.0252, respectively). Compared with placebo, trilaciclib significantly reduced DSN and SN, irrespective of G‐CSF administration. RBC transfusions and ESAs were most often administered in patients with grade 3/4 anemia; however, patients typically received RBC transfusions over ESA administration.

Conclusions

By improving CIM and reducing the need for associated supportive care, trilaciclib has the potential to reduce the burden of myelosuppression on patients receiving myelosuppressive chemotherapy for the treatment of ES‐SCLC.

Trial registration

ClinicalTrials.gov (NCT02499770; NCT03041311; NCT02514447).

Cyclin-dependent kinase (CDK) inhibitors in solid tumors: a review of clinical trials

Cyclin-dependent kinases (CDKs) play a key regulating role in the cell cycle, which is almost universally altered in cancer, leading to sustained proliferation. Early pan-CDK inhibitors showed poor results in clinical trials for solid malignancies, as the lack of selectivity produced significant toxicity. The production of more selective inhibitors led to significant developments in cancer therapy, as CDK4/6 inhibitors in combination with endocrine therapy changed the landscape of the treatment of hormone-receptor positive (HR +) metastatic breast cancer. Recently, Trilaciclib demonstrated benefits regarding hematological toxicity compared to placebo when administered in combination with chemotherapy in small cell lung cancer. Newer agents, such as SY-5609, a selective CDK7 inhibitor, have also shown promising results in early clinical trials. In this paper, we review the data from clinical trials of CDK inhibitors in solid tumors, either as a monotherapy or in combination with other agents, with an emphasis on novel agents and potential new indications for this drug class.

Exploratory composite endpoint demonstrates benefit of trilaciclib across multiple clinically meaningful components of myeloprotection in patients with small cell lung cancer

Chemotherapy-induced myelosuppression is an acute, dose-limiting toxicity of chemotherapy regimens used in the treatment of extensive-stage small cell lung cancer (ES-SCLC). Trilaciclib protects haematopoietic stem and progenitor cells from chemotherapy-induced damage (myeloprotection). To assess the totality of the myeloprotective benefits of trilaciclib, including analysis of several clinically relevant but low-frequency events, an exploratory composite endpoint comprising five major adverse haematological events (MAHE) was prospectively defined: all-cause hospitalisations, all-cause chemotherapy dose reductions, febrile neutropenia (FN), prolonged severe neutropenia (SN) and red blood cell (RBC) transfusions on/after Week 5. MAHE and its individual components were assessed in three randomised, double-blind, placebo-controlled Phase 2 trials in patients receiving a platinum/etoposide or topotecan-containing chemotherapy regimen for ES-SCLC and in data pooled from the three trials. A total of 242 patients were randomised across the three trials (trilaciclib, n = 123; placebo, n = 119). In the individual trials and the pooled analysis, administering trilaciclib prior to chemotherapy resulted in a statistically significant reduction in the cumulative incidence of MAHE compared to placebo. In the pooled analysis, the cumulative incidences of all-cause chemotherapy dose reductions, FN, prolonged SN and RBC transfusions on/after Week 5 were significantly reduced with trilaciclib vs placebo; however, no significant difference was observed in rates of all-cause hospitalisations. Additionally, compared to placebo, trilaciclib significantly extended the amount of time patients remained free of MAHE. These data support the myeloprotective benefits of trilaciclib and its ability to improve the overall safety profile of myelosuppressive chemotherapy regimens used to treat patients with ES-SCLC.

Improving Outcomes of Chemotherapy: Established and Novel Options for Myeloprotection in the COVID-19 Era

Chemotherapy-induced damage of hematopoietic stem and progenitor cells (HPSCs) often results in myelosuppression that adversely affects patient health and quality of life. Currently, chemotherapy-induced myelosuppression is managed with chemotherapy dose delays/reductions and lineage-specific supportive care interventions, such as hematopoietic growth factors and blood transfusions. However, the COVID-19 pandemic has created additional challenges for the optimal management of myelosuppression. In this review, we discuss the impact of this side effect on patients treated with myelosuppressive chemotherapy, with a focus on the prevention of myelosuppression in the COVID-19 era. During the COVID-19 pandemic, short-term recommendations on the use of supportive care interventions have been issued with the aim of minimizing the risk of infection, reducing the need for hospitalization, and preserving limited blood supplies. Recently, trilaciclib, an intravenous cyclin-dependent kinase 4 and 6 inhibitor, was approved to decrease the incidence of myelosuppression in adult patients when administered prior to platinum/etoposide-containing or topotecan-containing chemotherapy for extensive-stage small cell lung cancer (ES-SCLC). Approval was based on data from three phase 2 placebo-controlled clinical studies in patients with ES-SCLC, showing that administering trilaciclib prior to chemotherapy significantly reduced multilineage myelosuppression, with patients receiving trilaciclib having fewer chemotherapy dose delays/reductions and myelosuppression/sepsis-related hospitalizations, and less need for supportive care interventions, compared with patients receiving placebo. Several other novel agents are currently in clinical development for the prevention or treatment of multilineage or single-lineage myelosuppression in patients with various tumor types. The availability of treatments that could enable patients to maintain standard-of-care chemotherapy regimens without the need for additional interventions would be valuable to physicians, patients, and health systems.

Prophylaxis and treatment strategies for optimizing chemotherapy relative dose intensity

INTRODUCTION

A decrease in relative-dose intensity (RDI) of chemotherapy has been shown to be associated with poor patient outcomes in solid tumors and non-Hodgkin's lymphoma. The actual delivered chemotherapy dose received by patients can be influenced by dose reductions and treatment delays, often due to toxicities, most commonly chemotherapy-induced neutropenia (CIN).

AREAS COVERED

We review seminal evidence and more recent studies that have shown an association between higher RDI and improved patient survival. A smaller number of studies has shown no association between RDI and outcomes. These differences may be due to study limitations, including low power, differences in patient and disease characteristics, or the chemotherapeutic regimen. We describe guidelines recommendations to prevent and treat CIN with granulocyte-colony stimulating factor (G-CSF) and describe novel approaches to prevent neutropenia that are being developed that may provide greater value and be associated with fewer adverse events than standard G-CSF options.

EXPERT OPINION

Maintaining RDI is important to ensure optimal patient outcomes. This can be achieved through the proper administration of G-CSF prophylaxis and treatment. Newer agents in development to treat and/or prevent CIN are entering regulatory review and may potentially change the treatment landscape for CIN in the future.

Trilaciclib prior to chemotherapy and atezolizumab in patients with newly diagnosed extensive-stage small cell lung cancer: A multicentre, randomised, double-blind, placebo-controlled Phase II trial

Trilaciclib is an intravenous CDK4/6 inhibitor administered prior to chemotherapy to preserve haematopoietic stem and progenitor cells and immune system function from chemotherapy-induced damage (myelopreservation). The effects of administering trilaciclib prior to carboplatin, etoposide and atezolizumab (E/P/A) were evaluated in a randomised, double-blind, placebo-controlled Phase II study in patients with newly diagnosed extensive-stage small cell lung cancer (ES-SCLC) (NCT03041311). The primary endpoints were duration of severe neutropenia (SN; defined as absolute neutrophil count <0.5 × 109 cells per L) in Cycle 1 and occurrence of SN during the treatment period. Other endpoints were prespecified to assess the effects of trilaciclib on additional measures of myelopreservation, patient-reported outcomes, antitumour efficacy and safety. Fifty-two patients received trilaciclib prior to E/P/A and 53 patients received placebo. Compared to placebo, administration of trilaciclib resulted in statistically significant decreases in the mean duration of SN in Cycle 1 (0 vs 4 days; P < .0001) and occurrence of SN (1.9% vs 49.1%; P < .0001), with additional improvements in red blood cell and platelet measures and health-related quality of life (HRQoL). Trilaciclib was well tolerated, with fewer grade ≥3 adverse events compared with placebo, primarily due to less high-grade haematological toxicity. Antitumour efficacy outcomes were comparable. Administration of trilaciclib vs placebo generated more newly expanded peripheral T-cell clones (P = .019), with significantly greater expansion among patients with an antitumour response to E/P/A (P = .002). Compared with placebo, trilaciclib administered prior to E/P/A improved patients' experience of receiving treatment for ES-SCLC, as shown by reduced myelosuppression, and improved HRQoL and safety profiles.

The Individual Effects of Cyclin-Dependent Kinase Inhibitors on Head and Neck Cancer Cells-A Systematic Analysis

Cyclin-dependent kinase inhibitors (CDKi´s) display cytotoxic activity against different malignancies, including head and neck squamous cell carcinomas (HNSCC). By coordinating the DNA damage response, these substances may be combined with cytostatics to enhance cytotoxicity. Here, we investigated the influence of different CDKi´s (palbociclib, dinaciclib, THZ1) on two HNSCC cell lines in monotherapy and combination therapy with clinically-approved drugs (5-FU, Cisplatin, cetuximab). Apoptosis/necrosis, cell cycle, invasiveness, senescence, radiation-induced γ-H2AX DNA double-strand breaks, and effects on the actin filament were studied. Furthermore, the potential to increase tumor immunogenicity was assessed by analyzing Calreticulin translocation and immune relevant surface markers. Finally, an in vivo mouse model was used to analyze the effect of dinaciclib and Cisplatin combination therapy. Dinaciclib, palbociclib, and THZ1 displayed anti-neoplastic activity after low-dose treatment, while the two latter substances slightly enhanced radiosensitivity. Dinaciclib decelerated wound healing, decreased invasiveness, and induced MHC-I, accompanied by high amounts of surface-bound Calreticulin. Numbers of early and late apoptotic cells increased initially (24 h), while necrosis dominated afterward. Antitumoral effects of the selective CDKi palbociclib were weaker, but combinations with 5-FU potentiated effects of the monotherapy. Additionally, CDKi and CDKi/chemotherapy combinations induced MHC I, indicative of enhanced immunogenicity. The in vivo studies revealed a cell line-specific response with best tumor growth control in the combination approach. Global acting CDKi's should be further investigated as targeting agents for HNSCC, either individually or in combination with selected drugs. The ability of dinaciclib to increase the immunogenicity of tumor cells renders this substance a particularly interesting candidate for immune-based oncological treatment regimens.

Trilaciclib: First Approval

Trilaciclib (Cosela™) is a small-molecule, short-acting, inhibitor of cyclin-dependent kinases (CDK) 4 and 6 developed by G1 Therapeutics for its myeloprotection and potential antitumor efficacy and safety benefits in combination with cancer chemotherapy. CDKs govern cell cycle progression, and trilaciclib induces a transient, reversible G1 cell cycle arrest of proliferating haematopoietic stem and progenitor cells in bone marrow, thus protecting them from damage during chemotherapy. In February 2021, trilaciclib received its first approval in the USA to decrease the incidence of chemotherapy-induced myelosuppression in adult patients when administered prior to a platinum/etoposide-containing regimen or topotecan-containing regimen for extensive-stage small cell lung cancer (ES-SCLC). Clinical studies in breast cancer, colorectal cancer and small cell lung cancer are underway in several countries. This article summarizes the milestones in the development of trilaciclib leading to this first approval.

Effects of Trilaciclib on Chemotherapy-Induced Myelosuppression and Patient-Reported Outcomes in Patients with Extensive-Stage Small Cell Lung Cancer: Pooled Results from Three Phase II Randomized, Double-Blind, Placebo-Controlled Studies

BACKGROUND

Chemotherapy-induced myelosuppression (CIM) and its sequalae cause significant side effects and harm to quality of life. Trilaciclib is an intravenous CDK4/6 inhibitor that is administered prior to chemotherapy to protect hematopoietic stem and progenitor cells from chemotherapy-induced damage (myeloprotection).

PATIENTS AND METHODS

Data from three randomized, double-blind, placebo-controlled studies (NCT02499770, NCT03041311, and NCT02514447) were pooled to evaluate the effects of trilaciclib administered prior to standard-of-care chemotherapy (first-line etoposide plus carboplatin [E/P], first-line E/P plus atezolizumab, and second-/third-line topotecan) in patients with extensive-stage small cell lung cancer (ES-SCLC). The primary endpoints were duration of severe neutropenia (absolute neutrophil count < 0.5 × 10⁹ cells/L) in cycle 1 and occurrence of severe neutropenia. Additional prespecified endpoints further assessed the effect of trilaciclib on myeloprotection, health-related quality of life (HRQoL), antitumor efficacy, and safety.

RESULTS

Of 242 randomized patients, 123 received trilaciclib and 119 received placebo. Compared with placebo, administration of trilaciclib prior to chemotherapy resulted in significant decreases in most measures of multilineage CIM. The reduction in hematologic toxicity translated into the reduced need for supportive care interventions and hospitalizations due to CIM or sepsis and improvements in HRQoL domains related to the protected cell lineages, including fatigue, physical wellbeing, and functional wellbeing. Antitumor efficacy was similar for patients receiving trilaciclib or placebo.

CONCLUSION

Administering trilaciclib prior to chemotherapy resulted in clinically meaningful reductions in CIM and its consequences and improved patient HRQoL, with no impact on the antitumor efficacy of three individual chemotherapy regimens used in the first- or second-/third-line treatment of ES-SCLC.

Development of CDK4/6 Inhibitors: A Five Years Update

The inhibition of cyclin dependent kinases 4 and 6 plays a role in aromatase inhibitor resistant metastatic breast cancer. Three dual CDK4/6 inhibitors have been approved for the breast cancer treatment that, in combination with the endocrine therapy, dramatically improved the survival outcomes both in first and later line settings. The developments of the last five years in the search for new selective CDK4/6 inhibitors with increased selectivity, treatment efficacy, and reduced adverse effects are reviewed, considering the small-molecule inhibitors and proteolysis-targeting chimeras (PROTACs) approaches, mainly pointing at structure-activity relationships, selectivity against different kinases and antiproliferative activity.

Trilaciclib dose selection: an integrated pharmacokinetic and pharmacodynamic analysis of preclinical data and Phase Ib/IIa studies in patients with extensive-stage small cell lung cancer

Purpose

Trilaciclib is a first-in-class CDK4/6 inhibitor that transiently arrests hematopoietic stem and progenitor cells (HSPCs) in the G1 phase of the cell cycle to preserve them from chemotherapy-induced damage (myelopreservation). We report integrated analyses of preclinical and clinical data that informed selection of the recommended Phase II dose (RP2D) used in trilaciclib trials in extensive-stage small cell lung cancer (ES-SCLC).

Methods

A semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model developed from preclinical data guided selection of an optimal dose for G1 bone marrow arrest in a first-in-human Phase I study (G1T28-1-01). PK, PD, safety, and efficacy data from G1T28-1-01 and two Phase Ib/IIa studies (G1T28-02/-03) in ES-SCLC were analyzed to support RP2D selection.

Results

Model simulation of bone marrow arrest based on preclinical data predicted that a ≥ 192 mg/m² dose would induce a 40–50% decrease in total bone marrow proliferation in humans and almost 100% cell cycle arrest of cycling HSPCs. Consistent with this model, analysis of bone marrow aspirates in healthy volunteers after trilaciclib 192 mg/m² administration demonstrated almost 100% G1 arrest in HSPCs and 40% decrease in total bone marrow proliferation, with minimal toxicity. G1T28-02/-03 reported similar PK parameters with trilaciclib 200 mg/m² but slightly lower exposures than expected compared with healthy volunteers; consequently, 240 and 280 mg/m² doses were also tested to match healthy volunteer exposures. Based on PK and relevant safety data, 240 mg/m² was selected as the RP2D, which was also favored by myelopreservation endpoints in G1T28-02/-03.

Conclusion

Integrated PK/PD, safety, and efficacy data support 240 mg/m² as the RP2D for trilaciclib.

ClinicalTrials.gov Identifiers

NCT02243150; NCT02499770; NCT02514447.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04239-9.

CDK4/6 and MAPK-Crosstalk as Opportunity for Cancer Treatment

Despite the development of targeted therapies and novel inhibitors, cancer remains an undefeated disease. Resistance mechanisms arise quickly and alternative treatment options are urgently required, which may be partially met by drug combinations. Protein kinases as signaling switchboards are frequently deregulated in cancer and signify vulnerable nodes and potential therapeutic targets. We here focus on the cell cycle kinase CDK6 and on the MAPK pathway and on their interplay. We also provide an overview on clinical studies examining the effects of combinational treatments currently explored for several cancer types.