On November 26, 2018 G1 Therapeutics, Inc. (Nasdaq: GTHX), a clinical-stage oncology company, reported positive topline data from its randomized, double-blind, placebo-controlled Phase 2 trial evaluating trilaciclib in combination with chemotherapy and the checkpoint inhibitor Tecentriq (atezolizumab) as a treatment for 1L SCLC (Press release, G1 Therapeutics, NOV 26, 2018, View Source [SID1234531637]). Trilaciclib is a first-in-class myelopreservation therapy designed to improve outcomes of patients who receive chemotherapy by preserving hematopoietic stem and progenitor cell (HSPC) and immune system function.
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"The robust multi-lineage myelopreservation benefits of trilaciclib shown in this trial confirm the results we observed in our earlier trial in first-line small cell lung cancer," said Raj Malik, M.D., Chief Medical Officer and Senior Vice President, R&D. "Trilaciclib may also extend overall survival in patients receiving chemotherapy and Tecentriq, and we expect to report those data when available."
Key Multi-Lineage Myelopreservation Findings
Data from this randomized, double-blind, placebo-controlled Phase 2 trial demonstrated that trilaciclib reduced clinically relevant consequences of myelosuppression versus placebo when administered in combination with chemotherapy (etoposide and carboplatin) and Tecentriq across three lineages: neutrophils, red blood cells (RBCs) and platelets. Lymphocyte subset analyses are ongoing. Trilaciclib was well tolerated, with no Grade 4 trilaciclib-related treatment emergent adverse events (TEAEs) reported.
Key hematological results from the trilaciclib/chemotherapy/Tecentriq trial are shown in the table below, along with data from the company’s previously reported Phase 2 trial that evaluated trilaciclib in combination with the same chemotherapy regimen for treatment of 1L SCLC.
Endpoint
Trilaciclib or Placebo +
Chemo/Tecentriq
Trilaciclib or Placebo + Chemo
Placebo
N=53
Trilaciclib
N=54
%
Reduction P-value
Placebo
N=37
Trilaciclib
N=38
%
Reduction P-value
Neutrophils
Mean duration in days of severe neutropenia in cycle 1 (SD)* 4
(4.7)
0
(1.0)
100.0 % <0.0001** 3
(3.9)
0
(0.5)
100.0 % 0.0003
Pts w Grade 4 neutropenia* 26
(49.1%)
1
(1.9%)
96.1 % <0.0001** 16
(43.2%) 2
(5.3%)
87.7 % 0.0001
Pts w G-CSF administration 25
(47.2%)
16
(29.6%)
37.3 % 0.0686 24
(64.9%) 4
(10.5%)
83.8 % <0.0001
Number of G-CSF administrations per cycle 0.28 0.149 46.8 % 0.0135 0.44 0.07 84.1 % <0.0001
Pts w febrile neutropenia 3
(5.7%)
1
(1.9%)
66.7 % 0.3105 3
(8.1%)
1
(2.6%)
67.9 % 0.2773
RBCs
Pts w Grade 3/4 anemia 15
(28.3%) 10
(18.5%)
34.6 % 0.3243 7
(18.9%)
4
(10.5%)
44.4 % 0.2879
RBC transfusions on/after 5 weeks on study 11
(20.8%)
7
(13.0%)
37.5 % 0.2671 8
(21.6%)
2
(5.7%)
73.6 % 0.0615
Platelets
Pts w Grade 3/4 thrombocytopenia 20
(37.7%) 1
(1.9%)
95.0 % 0.0026 5
(13.5%)
4
(10.5%)
22.2 % 0.6888
Pts w Grade 4 thrombocytopenia 9
(17.0%) 0
(0.0%)
100.0 % 0.0017 0
(0.0%)
0
(0.0%)
NE NE
Pts w chemo dose reductions 14
(26.4%) 3
(5.6%)
78.8 % 0.0127 13
(35.1%) 3
(7.9%)
77.5 % 0.0033
Pts w Grade 3/4 hematologic TEAEs 38
(71.7%)
19
(36.5%)+
49.1 % 0.0016 27
(73.0%) 9
(23.7%)
67.5 % <0.0001
*
Primary endpoint in trilaciclib/chemotherapy/Tecentriq trial
Adjusted for multiplicity with one-sided significance level set at 0.025 by design; all other p-values are two-sided
+
52 patients were included in the safety population; 2 randomized patients did not receive treatment
Preliminary Anti-Tumor Efficacy Findings
Trilaciclib’s potential to preserve immune system function during chemotherapy may enhance overall survival (OS) in this trial. OS data are immature and will be reported when available.
There was no statistical difference between the trilaciclib and placebo groups in overall response rate (ORR) (trilaciclib 56.0%, placebo 63.5%) and median duration of response (DOR) (trilaciclib 5.2 months, placebo 4.2 months). Preliminary median progression-free survival (PFS) was 5.7 months for trilaciclib versus 5.4 months for placebo (hazard ratio 0.74, p=0.3025; less than 80% of events).
"We now have positive myelopreservation results from two randomized trials of trilaciclib in first-line small cell lung cancer, and later this year will report findings from two additional trials in different indications, metastatic triple-negative breast cancer and second-/third-line small cell lung cancer," said Mark Velleca, M.D., Ph.D., Chief Executive Officer. "We plan to request meetings with U.S. and European regulatory agencies in early 2019 to discuss the totality of our clinical data and potential pathways to approval."
Trial Design
This randomized, double-blind, placebo-controlled trial enrolled participants with a confirmed diagnosis of extensive-stage 1L SCLC. The trial randomized 107 treatment-naïve patients in a 1:1 ratio. Patients with ECOG Performance Status of 0-2 and asymptomatic brain metastases were eligible. All patients received a chemotherapy regimen of etoposide and carboplatin plus the checkpoint inhibitor Tecentriq (up to four cycles), followed by Tecentriq maintenance therapy. Patients were randomized to receive trilaciclib or placebo administered intravenously prior to each dose of chemotherapy.
Participants in both trial arms were able to receive standard supportive care as recommended by the clinical investigator. Growth factors, including granulocyte colony-stimulating factor (G-CSF) and erythropoietin, were available per American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) guidelines.
About Trilaciclib
Trilaciclib is a first-in-class myelopreservation therapy designed to improve outcomes of patients who receive chemotherapy by preserving hematopoietic stem and progenitor cell (HSPC) and immune system function. Trilaciclib is a short-acting intravenous CDK4/6 inhibitor administered prior to chemotherapy.
Trilaciclib is being evaluated in four randomized Phase 2 clinical trials. G1 has reported positive results from two of these trials, showing myelopreservation benefits in newly diagnosed, treatment-naive SCLC patients. In the first trial, trilaciclib was administered in combination with a chemotherapy regimen of etoposide and carboplatin (NCT02499770); topline data were released in March and additional data were reported at the European Society of Medical Oncology (ESMO) (Free ESMO Whitepaper) 2018 Congress. In the second trial, trilaciclib was administered in combination with the same chemotherapy regimen and the checkpoint inhibitor Tecentriq (atezolizumab) (NCT03041311); topline data were reported in November. The company plans to report data from two other randomized Phase 2 trials in 2018. Results from a trial in combination with chemotherapy in metastatic triple-negative breast cancer (NCT02978716) will be presented at the San Antonio Breast Cancer Symposium on December 5, 2018. The company plans to release topline data from a trial in combination with chemotherapy in previously treated SCLC (NCT02514447) by the end of 2018.
Webcast and Conference Call
The management team will host a webcast and conference call at 4:30 p.m. ET today to provide an overview of the trial findings and next steps for the trilaciclib development program. The live call may be accessed by dialing 866-763-6020 (domestic) or 210-874-7713 (international) and entering the conference code: 4156078. A live and archived webcast will be available on the Events & Presentations page of the company’s website: www.g1therapeutics.com.