Introduction
Trilaciclib, or G1T28, is a CDK4 and CDK6 inhibitor, indicated to reduce the incidence of chemotherapy induced myelosuppression in patients before topotecan-containing or platinum and etoposide-containing chemotherapy for extensive stage small cell lung cancer. CDK4 and CDK6 inhibitors have been investigated since the mid 1990s for their use in tumorigenesis and chemotherapy. Trilaciclib was first described in the literature in 2016.
Trilaciclib was granted FDA approval on 12 February 2021.
Uses
Trilaciclib is a CDK4 and CDK6 inhibitor to reduce the risk of chemotherapy induced myelosuppression.
Trilaciclib is indicated to reduce the incidence of chemotherapy induced myelosuppression in patients prior to receiving platinum and etoposide-containing or topotecan-containing chemotherapy regimens for extensive-stage small cell lung cancer.
Associated Conditions
Pharmacodynamics
Trilaciclib is indicated to reduce the incidence of chemotherapy induced myelosuppression in patients prior to receiving platinum and etoposide-containing or topotecan-containing chemotherapy regimens for extensive-stage small cell lung cancer. It has a short duration of action of approximately 16 hours, and a narrow therapeutic index. Patients should be counselled regarding the risk of injection site reactions, hypersensitivity, and interstitial lung disease.
Mechanism of Action
Trilaciclib is inhibits cyclin-dependant kinase 4 (CDK4) at a concentration of 1 nmol/L and cyclin-dependent kinase 5 (CDK5) at 4 nmol/L. Inhibition of CDK2, CDK5, and CDK7 is over 1000-fold less at these concentrations and inhibition of CDK9 is 50-fold less.
CDK4 and CDK5 are expressed in hematopoietic stem cells and progenitor cells. They are capable of phosphorylating and inactivating the retinoblastoma protien; a tumor suppressor. When trilaciclib is given to patients with retinoblastoma protein-null small cell lung cancer, it does not interfere with the intended chemotherapy induced cytotoxicity of cancer cells. Inhibition of CDK4 and CDK5 leads to a reversible pause in the cell cycle in the G1 phase for approximately 16 hours. The temporary cell cycle arrest prevents chemotherapy induced DNA damage in healthy cells, reducing the activity of caspases 3 and 7, which reduces apoptosis of healthy cells.
Other studies have shown inhibitors of CDK4 and CDK6 enhance T-cell activation, upregulating major histocompatibility complex (MHC) class I and II, and stabilize programmed death-ligand 1 (PD-L1). Together these activities increase T-cell activity, increase antigen presentation, and sensitize cells to immune checkpoint inhibitors.
Absorption
Cmax and AUC of trilaciclib increase proportionally with dose.
Volume of Distribution
The volume of distribution of trilaciclib at steady state is 1130 L.
Protein Binding
Data regarding the protein binding of trilaciclib are not readily available.
Route of Elimination
79.1% of a radiolabelled dose is recovered in the feces, 7% as the unchanged parent compound. 14% of a radiolabelled dose is recovered in the urine, 2% as the unchanged parent compound.
Half Life
The mean terminal half life of trilaciblib is approximately 14 h.
Clearance
The clearance of trilaciclib is 158 L/h.
Toxicity
Data regarding overdoses of trilaciclib are not readily available. For grade 3 or worse injection site reactions, acute drug hypersensitivity reactions, and interstitial lung disease; or any other grade 4 toxicities; permanently discontinue trilacilib.
Food Interactions
No interactions found.
Dosage
Missed Treatment Session(s): If the Trilaciclib dose is missed, discontinue chemotherapy on the day the Trilaciclib dose was missed. Consider resuming both Trilaciclib and chemotherapy on the next scheduled day for chemotherapy.
Discontinuation of Treatment: If Trilaciclib is discontinued, wait 96 hours from the last dose of Trilaciclib before resumption of chemotherapy only.
Preparation & Administration: Reconstitute and further dilute Trilaciclib prior to intravenous infusion as outlined below. Use aseptic technique for reconstitution and dilution. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.