Clinical Pharmacology for Cosela
Mechanism Of Action
Trilaciclib is a transient inhibitor of CDK 4 and 6. Hematopoietic stem and progenitor cells (HSPCs) in the bone marrow give rise to circulating neutrophils, RBCs, and platelets. HSPC proliferation is dependent on CDK4/6 activity.
Pharmacodynamics
Bone Marrow
Trilaciclib exhibited dose-dependent inhibition of CD45+/CD3+ lymphocyte proliferation following administration of single-dose COSELA 96 or 192 mg/m² (0.4 or 0.8 times the approved recommended dose) in healthy subjects.
Trilaciclib increased the percentage of cells arrested in G1 up to 32 hours post-infusion for all bone marrow progenitor subsets evaluated (hematopoietic stem cell/multipotent progenitor, oligopotent progenitor, monocyte lineage, granulocyte lineage, erythroid lineage, and megakaryocyte lineage) following a single dose of COSELA 192 mg/m² (0.8 times the approved recommended dose) in healthy subjects. Partial recovery of the total bone marrow with resumption of proliferation of the bone marrow progenitor subsets was observed by 32 hours post-dose. This transient G1 arrest of hematopoietic stem cells contributed to the myeloprotective effect of trilaciclib.
Cardiac Electrophysiology
COSELA is associated with dose-dependent and delayed increase in the QTc interval. The underlying mechanism of the delayed QT effect is unknown. At the clinical dose of 240 mg/m², COSELA did not have a clinically relevant effect on QTc (i.e., >10 msec). QTc prolongation was observed at higher doses.
Pharmacokinetics
The maximum concentration (Cmax) increased proportionally whereas the total plasma exposure (AUC0-last) increased slightly greater than proportional over a dosage range of trilaciclib 200 mg/m² to 700 mg/m² (0.83 to 2.9 times the approved recommended dose). There was no accumulation of trilaciclib following repeated dosing.
Distribution
The in vitro human plasma protein binding of trilaciclib is 69% and appeared independent of trilaciclib concentration from 0.75 to 3.0 μg/mL. The blood/plasma ratio ranged from 1.21 to 1.53 for trilaciclib across concentrations of 0.5 μg/mL to 50 μg/mL in vitro. The volume of distribution at steady state was 1130 L.
Elimination
The mean terminal half-life of trilaciclib is approximately 14 hours. Clearance was estimated to be 158 L/hr.
Metabolism
Trilaciclib undergoes extensive metabolism. Trilaciclib is the predominant circulating compound in plasma following intravenous administration, representing ~50% of plasma total radioactivity. In vitro studies indicated that trilaciclib is primarily metabolized by aldehyde oxidase (AO), cytochrome P450 (CYP) 3A4 and CYP2C8.
Excretion
After a single dose of radiolabeled trilaciclib 192 mg/m² (0.8 times the approved recommended dosage), approximately 79.1% of the dose was recovered in feces (7% unchanged) and 14% was recovered in urine (2% unchanged).
Trilaciclib is eliminated mainly via the fecal route, with a small contribution of the renal route.
Specific Populations
No clinically significant differences in the pharmacokinetics of trilaciclib were observed based on age (range: 19 to 80 years), sex, race, mild to moderate renal impairment (30 to 89 mL/min/1.73 m² measured by estimated glomerular filtration rate [eGFR]), or mild hepatic impairment (total bilirubin ≤ULN and AST >ULN, or total bilirubin >1.0 to 1.5 × ULN, irrespective of AST). The effect of severe renal impairment (<30 mL/min/1.73 m²), end stage renal disease, or dialysis on trilaciclib pharmacokinetics has not been studied.
Subjects With Hepatic Impairment
Trilaciclib unbound AUCinf increased by 40% and 63%, respectively, in subjects with moderate and severe hepatic impairment (Child-Pugh classes B and C). No clinically significant differences were observed in trilaciclib systemic exposures in subjects with mild hepatic impairment [see DOSAGE AND ADMINISTRATION and Use In Specific Populations].
Drug Interaction Studies
Clinical Studies
Cytochrome P450 (CYP) Enzymes
There were no clinically significant differences in trilaciclib pharmacokinetics when used concomitantly with itraconazole (strong CYP3A inhibitor) or rifampin (strong CYP3A inducer). There were no clinically significant differences in midazolam (CYP3A substrate) pharmacokinetics when used concomitantly with trilaciclib.
Transporter Systems
Concomitant use of trilaciclib increased metformin (OCT2, MATE1, and MATE-2K substrate) AUCinf and Cmax by approximately 65% and 81%, respectively. Renal clearance of metformin was decreased by 37%. There were no clinically significant differences in topotecan (MATE1 and MATE-2K substrate) pharmacokinetics when used concomitantly with trilaciclib.
In Vitro Studies
CYP Enzymes
Trilaciclib did not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, or CYP2D6. Trilaciclib is an inducer for CYP1A2, and is not an inducer for CYP2B6 or CYP3A4.
Transporter Systems
Trilaciclib did not inhibit P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, OAT1, or OAT3. Trilaciclib was a substrate of BCRP and P-gp, but not bile salt export pump (BSEP), MATE1, MATE-2K, or OCT.
Clinical Studies
The efficacy of COSELA was established in three randomized, double-blind, placebo-controlled trials in patients with extensive stage-small cell lung cancer (ES-SCLC). Study 1 (G1T28-05; NCT03041311) enrolled adult patients receiving carboplatin, etoposide, and atezolizumab for newly diagnosed ES-SCLC. Study 2 (G1T28-02; NCT02499770) enrolled adult patients receiving etoposide/carboplatin for newly diagnosed ES-SCLC. Study 3 (G1T28-03; NCT02514447) enrolled adult patients receiving topotecan for previously treated ES-SCLC.
During Cycle 1, all three studies prohibited primary prophylactic granulocyte-colony stimulating factor (G-CSF) and erythropoiesis-stimulating agent (ESA) use. Both ESAs and prophylactic G-CSF were allowed from Cycle 2 onwards as clinically indicated. Therapeutic G-CSF, RBC, and platelet transfusions were allowed at any time during the studies as clinically indicated.
Study 1: COSELA Prior To Etoposide, Carboplatin, And Atezolizumab (E/P/A)
Patients With Newly Diagnosed ES-SCLC Not Previously Treated With Chemotherapy
Study 1 (G1T28-05) was a randomized (1:1), double-blind, placebo-controlled study of COSELA or placebo administered prior to treatment with etoposide, carboplatin, and atezolizumab (E/P/A) for patients with newly diagnosed ES-SCLC not previously treated with chemotherapy.
A total of 107 patients were randomized to receive COSELA (n=54) or placebo (n=53) prior to administration of E/P/A; patients were stratified by Eastern Cooperative Oncology Group (ECOG) performance status (0 to 1 vs 2) and the presence of brain metastases. Carboplatin (AUC 5) and atezolizumab (1200 mg) were administered on Day 1 and etoposide (100 mg/m²) and COSELA (240 mg/m²) or placebo were administered on Days 1, 2, and 3 of a 21-day cycle for a maximum of 4 cycles (induction). After induction, maintenance atezolizumab (1200 mg) monotherapy on Day 1 of a 21-day cycle continued until disease progression or unacceptable toxicity. COSELA was not administered during maintenance.
The study population characteristics were: median age 64 years (range: 45 to 83); 70% male; 97% white; 14% ECOG performance status 2; 28% with a history of brain metastases; 38% current smokers; 46% lactate dehydrogenase (LDH) >ULN.
The mean relative dose intensities (RDIs) for E/P/A in patients receiving COSELA were 93%, 95%, and 93%, respectively. The mean RDIs for E/P/A in patients receiving placebo were 88%, 89%, and 91%, respectively. Dose reductions of carboplatin occurred in 2% of patients receiving COSELA and in 25% of patients receiving placebo; dose reductions of etoposide occurred in 6% of patients receiving COSELA and in 26% of patients receiving placebo. No dose reduction was allowed for COSELA or atezolizumab.
The study demonstrated a statistically significantly shorter duration of severe neutropenia (DSN) in Cycle 1 (0 vs 4 days) and a lower proportion of patients with severe neutropenia (SN) (2% vs 49%) in patients receiving COSELA compared with placebo (Table 5). Nineteen percent of patients receiving COSELA had Grade 3 or 4 decreased hemoglobin compared with 28% of patients receiving placebo (adjusted relative risk 0.663 [95% CI: 0.336, 1.310]). The rate of RBC transfusions over time was 1.7/100 weeks for patients receiving COSELA and 2.6/100 weeks for patients receiving placebo (adjusted relative risk was not estimable). Six percent of patients receiving COSELA received erythropoiesis-stimulating agents (ESAs) compared with 11% of patients receiving placebo (adjusted relative risk 0.529 [95% CI: 0.145, 1.927]).
Table 5: Study 1: Myeloprotective Efficacy Results in Patients Treated with COSELA or Placebo Prior to Chemotherapy (Intent-to-Treat Analysis)
| Endpoint |
COSELA 240 mg/m²
(N=54) |
Placebo
(N=53) |
Treatment Effect3 (Mean Difference* or Adjusted Relative Risk) (95% CI) |
Adjusted 1-sided p-valueb |
| Primary Endpoints |
| DSN in Cycle 1 (days): mean (SD) |
0 (1.0) |
4 (4.7) |
-3.6* (-4.9, -2.3) |
<0.0001 |
| Number (%) of patients with severe neutropenia |
1 (1.9%) |
26 (49.1%) |
0.038
(0.008, 0.195) |
<0.0001 |
| Key Secondary Endpoints |
| Number of all-cause dose reductions, event rate per cycle |
0.021 |
0.085 |
0.242
(0.079, 0.742) |
0.0195 |
| Number (%) of patients with RBC transfusion on/after 5 weeks |
7 (13.0%) |
11 (20.8%) |
0.642
(0.294, 1.404) |
-- |
| Number (%) of patients with G-CSF administration |
16 (29.6%) |
25 (47.2%) |
0.646
(0.403, 1.034) |
-- |
ÂANCOVA=analysis of covariance; CI=confidence interval; DSN=duration of severe neutropenia; G-CSF=granulocyte colony-stimulating factor; N=total number of patients in each treatment group; RBC=red blood cell; SD=standard deviation
a The following statistical models were used to assess treatment effects: non-parametric ANCOVA (DSN in Cycle 1); modified Poisson regression (occurrence of SN and RBC transfusion on/after 5 weeks); negative binomial regression (number of all-cause dose reductions). All models included the following as covariates: ECOG status, presence of brain metastases, and the corresponding baseline laboratory values.
b One-sided adjusted p-value obtained from a Hochberg-based gatekeeping procedure. |
Study 2: COSELA Prior To Etoposide And Carboplatin
Patients With Newly Diagnosed ES-SCLC Not Previously Treated With Chemotherapy
Study 2 (G1T28-02) was a randomized (1:1), double-blind, placebo-controlled evaluation of COSELA or placebo administered prior to treatment with etoposide and carboplatin (E/P) for patients with newly diagnosed ES-SCLC not previously treated with chemotherapy. A total of 77 patients were randomized to COSELA (n=39) or placebo (n=38) and stratified by ECOG performance status (0 to 1 vs 2). Carboplatin (AUC 5) was administered on Day 1 and etoposide (100 mg/m²) and COSELA (240 mg/m²) or placebo were administered on Days 1, 2, and 3 of a 21-day cycle until disease progression or unacceptable toxicity.
Ten percent of patients receiving COSELA had Grade 3 or 4 decreased hemoglobin compared with 18% of patients receiving placebo. The rate of RBC transfusions over time was 0.5/100 weeks for patients receiving COSELA and 1.9/100 weeks for patients receiving placebo. Three percent of patients receiving COSELA received ESAs compared with 5% of patients receiving placebo.
Table 6: Study 2: Myeloprotective Efficacy Results in Patients Treated with COSELA or Placebo Prior to Chemotherapy (Intent-to-Treat Analysis)
| Endpoint |
COSELA 240 mg/m²
(N=39) |
Placebo
(N=38) |
| DSN in Cycle 1 (days): mean (SD) |
0 (0.5) |
3 (3.9) |
| Number (%) of patients with severe neutropenia |
2 (5.1%) |
16 (42.1%) |
| Number of all-cause dose reductions, event rate per cycle |
0.022 |
0.084 |
| Number (%) of patients with RBC transfusion on/after 5 weeks |
2 (5.1%) |
9 (23.7%) |
| Number (%) of patients with G-CSF administration |
4 (10.3%) |
24 (63.2%) |
| DSN=duration of severe neutropenia; G-CSF=granulocyte colony-stimulating factor; N=total number of patients in each treatment group; RBC=red blood cell; SD=standard deviation |
Study 3: COSELA Prior To Topotecan
Patients With ES-SCLC Previously Treated With Chemotherapy
Study 3 (G1T28-03) included a randomized, double-blind, placebo-controlled evaluation of COSELA or placebo administered prior to topotecan in patients with ES-SCLC previously treated with chemotherapy. A total of 61 patients were randomized to COSELA (n=32) or placebo (n=29). Patients were stratified by ECOG performance status (0 to 1 vs 2) and sensitivity to first-line treatment. Topotecan (1.5 mg/m²) and COSELA (240 mg/m²) or placebo were administered on Days 1-5 of a 21-day cycle. Treatment was administered until disease progression or unacceptable toxicity.
Thirty-eight percent of patients receiving COSELA had Grade 3 or 4 decreased hemoglobin compared with 59% of patients receiving placebo. The rate of RBC transfusions over time was 2.6/100 weeks for patients receiving COSELA and 6.3/100 weeks for patients receiving placebo. Three percent of patients receiving COSELA received ESAs compared with 21% of patients receiving placebo.
Table 7: Study 3: Myeloprotective Efficacy Results in Patients Treated with COSELA or Placebo Prior to Chemotherapy (Intent-to-Treat Analysis)
| Endpoint |
COSELA 240 mg/m²
(N=32) |
Placebo
(N=29) |
| Primary Endpoints |
| DSN in Cycle 1 (days): mean (SD) |
2 (3.9) |
7 (6.2) |
| Number (%) of patients with severe neutropenia |
13 (40.6%) |
22 (75.9%) |
| Key Secondary Endpoints |
| Number of all-cause dose reductions, event rate per cycle |
0.051 |
0.116 |
| Number (%) of patients with RBC transfusion on/after 5 weeks |
10 (31.3%) |
12 (41.4%) |
| Number (%) of patients with G-CSF administration |
16 (50.0%) |
19 (65.5%) |
| Number (%) of patients with platelet transfusion |
8 (25.0%) |
9 (31.0%) |
| DSN=duration of severe neutropenia; G-CSF=granulocyte colony-stimulating factor; N=total number of patients in each treatment group; RBC=red blood cell; SD=standard deviation |
Patient Subgroups
Treatment efficacy was examined across different subgroups, including those quantifying the risk of febrile neutropenia, anemia, and RBC transfusions; results were consistent across subgroups.