Phase 1 Study of the Efficacy and Safety of Ramucirumab in Combination with Osimertinib in Advanced T790M-Positive EGFR-Mutant Non-Small Cell Lung Cancer

Abstract

Purpose:

We report the final analysis of JVDL (NCT02789345), which examined the combination of the EGFR TKI osimertinib plus the VEGFR2-directed antibody ramucirumab in patients with T790M-positive EGFR-mutant NSCLC.

Patients and Methods:

This open-label, single-arm phase 1 study enrolled patients with EGFR T790M-positive NSCLC, who had progressed following EGFR TKI but were third-generation EGFR TKI-naïve. A dose-limiting toxicity (DLT) period with as-needed dose de-escalation was followed by an expansion cohort. Patients received daily oral osimertinib and intravenous ramucirumab every 2 weeks until progression or discontinuation.

Results:

Twenty-five patients were enrolled. No DLTs were observed. Median follow-up time was 25.0 months. Common Grade 3 or higher treatment-related adverse events (TRAEs) were hypertension (8%) and platelet count decreased (16%); Grade 5 TRAE (subdural hemorrhage) occurred in one patient. Patients with (N=10) and without CNS metastasis (N=15) had similar safety outcomes. Five patients remain on treatment. Objective response rate (ORR) was 76%. Median duration of response was 13.4 months (90% CI: 9.6-21.2). Median progression-free survival (PFS) was 11.0 months (90% CI: 5.5-19.3). Efficacy was observed in patients with and without CNS metastasis (ORR 60% and 87%; median PFS 10.9 and 14.7 months, respectively). Exploratory biomarker analyses in circulating tumor DNA suggested that on-treatment loss of EGFR Exon 19 deletion or L858R mutations, detectable at baseline, correlated with longer PFS, but on-treatment loss of T790M did not. Emergent genetic alterations post progression included C797S, MET amplification, and EGFR amplification.

Conclusions:

Ramucirumab plus osimertinib demonstrated encouraging safety and antitumor activity in T790M-positive EGFR-mutant NSCLC.

Statement of Translational Relevance

Osimertinib, an EGFR TKI, is an effective treatment in patients with metastatic EGFR-mutant NSCLC, but the development of resistance is universal. This phase 1 study reports the evaluation of osimertinib plus ramucirumab, a VEGFR2 monoclonal antibody, in advanced T790M-positive EGFR-mutant NSCLC, with previous progression on EGFR TKI. This was the first ramucirumab study that included patients with untreated CNS metastasis. The combination was tolerable and exhibited a safety profile consistent with each drug individually with no additive toxicities. The combination demonstrated antitumor activity in patients with and without CNS metastasis. Exploratory biomarker analyses in circulating tumor DNA suggested that on-treatment loss of EGFR Exon 19 deletion or L858R mutations, detectable at baseline, correlated with longer PFS, but on-treatment loss of T790M did not. This study also explored emergent genetic alterations post progression. Dual targeting of EGFR and VEGFR pathways is a promising new treatment strategy for EGFR-mutant NSCLC.

Introduction

Lung cancer is the leading cause of cancer-related mortality (1), with non-small cell lung cancer (NSCLC) accounting for approximately 85% of all lung cancers (2). Activating mutations in epidermal growth factor receptor (EGFR), such as Exon 19 deletion or Exon 21 L858R mutation, are detected in approximately 20% of advanced NSCLC (3). EGFR tyrosine kinase inhibitors (TKIs) significantly improve progression-free survival (PFS) and improve other efficacy parameters including overall survival (OS) compared with platinum-based chemotherapy in patients with metastatic NSCLC whose tumors have sensitizing EGFR mutations (4-6). However, patients with EGFR mutation-positive NSCLC eventually progress on first- and second-generation EGFR TKI treatment, commonly due to the acquisition of a secondary EGFR Exon 20 T790M mutation (7). Osimertinib, a third-generation EGFR TKI with selectivity for both sensitizing EGFR mutations and the T790M mutation over the wild-type EGFR (8), has been shown to be safe and effective in patients with metastatic EGFR T790M mutation-positive NSCLC who have progressed on or after EGFR TKI therapy (9-11). Recently, osimertinib has been shown to have superior efficacy over gefitinib/erlotinib as a first-line treatment for advanced NSCLC (12-14).

Despite promising initial results, the eventual development of resistance to osimertinib is universal, underscoring the need for novel combinations of osimertinib with other anticancer agents that confer improved efficacy and more durable responses for the long-term management of EGFR-mutant NSCLC (15). Combination regimens pairing an EGFR TKI with an antiangiogenic agent have shown encouraging results in EGFR-mutant NSCLC (16-19). Ramucirumab, a human immunoglobulin G subclass 1 monoclonal antibody against vascular endothelial growth factor receptor-2 (VEGFR2) that blocks binding of the VEGFA, VEGFC, and VEGFD ligands, has been shown to have antitumor activity in the treatment of several solid tumor types both as monotherapy (20-22) and in combination with other anticancer treatments (17,23-26). In patients with stage IV NSCLC who have progressed on platinum-based therapy, the phase 3 REVEL study demonstrated that ramucirumab in combination with docetaxel in the second-line setting improved PFS, OS, and response rate over placebo plus docetaxel (23). Notably, the phase 3 RELAY study recently showed that ramucirumab plus the EGFR TKI erlotinib had superior PFS compared with placebo plus erlotinib in patients with untreated EGFR-mutant metastatic NSCLC (17).

The objective of the current study was to determine the safety, preliminary efficacy, and pharmacokinetics of osimertinib with ramucirumab in patients with advanced T790M-positive EGFR-mutant NSCLC, with previous progression on a first- or second-generation EGFR TKI, as this study was initiated before the approval of osimertinib in the first-line setting.

Many patients with NSCLC develop central nervous system (CNS) metastasis (27,28), and osimertinib has previously demonstrated CNS and systemic efficacy in patients with EGFR-mutant NSCLC (14,29,30). Preclinical and clinical studies have suggested the involvement of angiogenesis in metastasis of NSCLC to the brain and the CNS activity and efficacy of VEGF inhibitors in NSCLC (31-38). Therefore, planned exploratory analyses aimed to examine the safety and efficacy of ramucirumab plus osimertinib in patients with and without CNS metastasis. In addition, circulating tumor DNA (ctDNA) in plasma samples was analyzed at baseline, on treatment, and after disease progression, to explore and correlate genetic alterations identified with efficacy.

Patients and Methods

Patients

This analysis includes patients who completed the ramucirumab plus osimertinib arm of the phase 1 JVDL study (ClinicalTrials.gov identifier: NCT02789345). The results of a necitumumab plus osimertinib treatment arm have been previously reported (39).

Eligible patients were at least 18 years old with locally advanced or metastatic NSCLC; Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 or 1; measureable disease as defined by the Response Evaluation Criteria In Solid Tumors Version 1.1 (RECIST 1.1) (40); disease progression immediately following first-line EGFR TKI treatment regardless of prior chemotherapy; documented evidence of lung cancer with one of the two common EGFR mutations known to be associated with EGFR TKI sensitivity (Exon 19 deletion or Exon 21 L858R mutation), and T790M-positive status using a validated test, including but not limited to those approved by the Food and Drug Administration (FDA) (e.g., Cobas^® EGFR Mutation Test Version 2) in the United States or recommended in the Summary of Product Characteristics for osimertinib in the European Union, performed locally after disease progression on EGFR TKI treatment. Patients who had CNS metastases were eligible if the disease was asymptomatic and stable, requiring no steroids or anticonvulsants for ≥2 weeks prior to receiving treatment; patients receiving radiotherapy needed to have completed ≥4 weeks prior to receiving treatment. Patients were not eligible if they had received prior treatment with osimertinib or another third-generation EGFR TKI or had a recent clinically significant illness or medical condition, including clinically active interstitial lung disease, inadequate organ function (hepatic, hematologic, coagulation, renal), or unresolved toxicity from prior systemic cancer therapy, surgery, or radiotherapy.

All studies were conducted with the approval of independent ethics committees at all participating centers and in accordance with the Declaration of Helsinki and the Good Clinical Practice guidelines. All patients provided written, informed consent.

Study Design and Treatments

This was an open-label, single-arm phase 1 study comprising a dose-finding portion (phase 1a) and a dose-expansion portion (phase 1b). Phase 1a followed a dose de-escalation 3+3 design, wherein dose level 0 was daily oral osimertinib (80 mg; fixed) and 10 mg/kg intravenous (IV) ramucirumab on Day 1, every two weeks for 2 cycles (for dose level −1, ramucirumab was to be reduced to 8 mg/kg IV). Results of the interim analysis from phase 1a were used to determine the dosing regimen for the expansion cohort in phase 1b. In both portions of the study, patients continued treatment until confirmed progressive disease (PD), unacceptable toxicity, or discontinuation for any other reason. Dose adjustments, delays, and omissions of the study drugs were allowed to manage adverse events (AEs) or other toxicities. Final analysis was conducted at the time of study completion, which was defined as approximately 2 years after enrollment of the last patient.

Outcomes

The primary objective of the phase 1a (dose-finding) portion of the study was to assess safety and tolerability of ramucirumab plus osimertinib, specifically assessing dose-limiting toxicities (DLTs) during the first 2 cycles (4 weeks) of treatment. DLTs were based on the incidence, intensity, and duration of AEs, which were graded based on the National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.0 (NCI CTCAE v.4.0). A DLT was defined as any Grade ≥3 nonhematologic toxicity (excluding elevation in liver aminotransferase or alanine aminotransferase of <7-days duration, renal function test elevations of <7-days duration, and skin rash persisting <14 days); Grade 4 hematologic toxicities lasting ≥7 days; Grade 3 or 4 thrombocytopenia if associated with bleeding; febrile neutropenia; and Grade 5 toxicity (death) if considered related to study treatment.

The primary objective of the phase 1b (dose-expansion) portion was additional assessment of safety and tolerability of ramucirumab in combination with osimertinib. Key secondary objectives were the assessment of preliminary efficacy, based on investigator-assessed objective response rate (ORR), disease control rate (DCR), duration of response (DOR), OS, and PFS. A secondary objective of both portions of the study was the assessment of the pharmacokinetics of the treatment regimen. Baseline tumor imaging occurred within 28 days of the first study dose and tumor response was assessed by the investigator every 6 weeks (±7 days) for 24 weeks and then every 12 weeks (±7 days) thereafter until disease progression, per RECIST v1.1. To confirm partial or complete response, a repeat tumor-imaging assessment occurred 4 weeks, at the earliest, after the first indication of response or at the next scheduled scan (i.e., 6 weeks ± 7 days later), whichever was clinically indicated. Magnetic resonance imaging or computed tomography scans of the brain with contrast were performed prior to enrollment at baseline for all patients and then to the above schedule if a patient had baseline CNS metastasis or if clinically warranted. The same imaging technique was used throughout the study for each patient.

Pharmacokinetics

Blood samples for assessment of ramucirumab concentration in serum were obtained at scheduled times on Day 1 of Cycles 2, 4, 5, 7, and 13 prior to ramucirumab infusion (trough or minimum ramucirumab concentration [C_min]) and at 1 hour after the end of ramucirumab infusion on Day 1 of Cycle 1 (approximate peak or maximum ramucirumab concentration [C_max]). Serum concentrations of ramucirumab were measured using a validated assay (41).

Exploratory Biomarker Assessments

Plasma samples were collected for assessment of ctDNA at baseline, during treatment (Cycle 4 Day 1 or Cycle 7 Day 1), and post progression (30-day follow-up). Genetic alterations were assessed by Guardant 360^® next-generation sequencing and are reported among patients with any detectable alteration using descriptive statistics.

Statistical Analyses

All patients who received at least one dose of study treatment were evaluated for safety and DLTs. Exposure was assessed by the number of cycles of treatment received, duration of treatment, dose delays, and dose intensity. Treatment-emergent adverse events (TEAEs), possible treatment-related AEs (TRAEs), serious AEs (SAEs), SAEs related to treatment, and AEs of special interest (AESIs) were listed and summarized using Medical Dictionary for Regulatory Activities Version 22 (MedDRA v.22) terminology and graded based on NCI CTCAE v.4.0 criteria.

Efficacy analyses included all patients enrolled in the dose-finding and dose-expansion portions of the study. Best overall systemic response and best overall intracranial response were recorded from the start of treatment until disease progression, in the order of complete response (CR), partial response (PR), and stable disease (SD) for all patients evaluable for efficacy, whose disease was assessable by RECIST 1.1. ORR (percentage of enrolled patients with a best response of PR or CR) and DCR (percentage of enrolled patients with a best response of PR, CR, or SD) were estimated and reported with exact 90% confidence intervals (CIs; based on the Clopper-Pearson method) for each arm. PFS, OS, and DOR were estimated using the Kaplan-Meier method (42), including the median and the associated 90% CI (unless otherwise indicated). PFS time was defined as the time from the date of first study treatment until the date of radiographic documentation of progression (as defined by RECIST 1.1), based on investigator assessment, or the date of death, whichever was earlier. OS was defined as the time from the date of first study treatment to the date of death from any cause. DOR was defined from the date of first documented CR or PR (responder) to the date of objective progression or the date of death due to any cause, whichever was earlier. Both safety and efficacy outputs were summarized across all patients in the dose-finding portion and expansion cohort and by subcategories based on the presence or absence of CNS metastases at baseline.

Results

Patient disposition, characteristics, and cumulative exposure

The data cut-off date was April 19, 2019. Between October 24, 2016, and April 20, 2017, 25 patients were enrolled in the study. Three patients were enrolled into the dose-finding portion, and no DLT was observed. Subsequently, 22 patients were enrolled into the dose-expansion portion. All 25 patients received at least 1 dose of study treatment (ramucirumab plus osimertinib). At the time of data cut-off, 20 of 25 (80%) patients had discontinued treatment (Supplementary Figure S1). The median OS follow-up time was 25.0 months (90% CI: 24.0-25.6; minimum-maximum: 0.7-28.4 months). The most common reason for treatment discontinuation was progressive disease (n=15; 60%). In addition, 1 patient discontinued due to a TRAE (congestive heart failure), and 1 patient died while on treatment due to cardiogenic pulmonary edema, deemed unrelated to treatment by the investigator.

The majority of patients were female (n=18; 72%) and Asian (n=13; 52%), with a median age of 64 years (Table 1). Most patients had adenocarcinoma (n=21; 84%); 3 (12%) patients had NSCLC not otherwise specified, and 1 (4%) patient had squamous cell carcinoma of lung, Stage IV disease at diagnosis (n=21; 84%), and an ECOG PS of 1 (n=22; 88%). The majority of patients (n=17; 68%) had tumors positive for EGFR Exon 19 deletion whereas 8 patients (32%) had EGFR Exon 21 L858R mutation-positive tumors. CNS metastases were present at baseline in 10 (40%) patients, 7 (70%) of whom had received prior radiotherapy.

Table 1.

Demographics and Baseline Clinical Characteristics – All Enrolled Patients

	n (%), except where indicated	All Patients (N=25)
Sex	Female	18 (72)
Age (years)	Median (range)	64 (45-80)
Race	Asian	13 (52)
	White	12 (48)
Histology
	Adenocarcinomaa	21 (84)
	NSCLCb	3 (12)
	Squamous cell carcinoma of the lung	1 (4)
Initial disease stage at diagnosis	Stage IA	1 (4)
	Stage IB	1 (4)
	Stage IIIA	1 (4)
	Stage IIIB	1 (4)
	Stage IV	21 (84)
Tobacco use	Current	1 (4)
	Former	7 (28)
	Never	17 (68)
ECOG PS	0	3 (12)
	1	22 (88)
CNS metastasis	No	15 (60)
	Yesc	10 (40)
EGFR mutation	Exon 19 deletion	17 (68)
	Exon 21 L858R	8 (32)

^a20 of 21 patients had lung adenocarcinoma

^bnot otherwise specified

^c3 of 10 patients with CNS metastasis had no prior radiotherapy (see Supplementary Table S5)

Data shown as n (%) unless otherwise noted.

CNS, central nervous system; ECOG PS, Eastern Cooperative Oncology Group Performance Status; EGFR, epidermal growth factor receptor; N, number of subjects in population; n, number of patients in specified category; NSCLC, non-small-cell lung cancer.

All patients received one or more doses of study treatment. The recommended dose for the expansion cohort was the initial dose level from the dose-finding portion of the study, i.e., 10 mg/kg ramucirumab IV every 2 weeks with oral 80 mg osimertinib once daily. At final analysis, median therapy duration was 13 cycles (interquartile range [IQR]: 6-30) for ramucirumab and 20 cycles (IQR: 7-30) for osimertinib. Median duration of therapy was 182 days (range: 19-770 days) for ramucirumab and 339 days (range: 17-779 days) for osimertinib. Overall, the median dose intensity for ramucirumab was 279 mg/week (IQR: 218-310 mg/week) and the median dose intensity for osimertinib was 560 mg/week (IQR: 560-560 mg/week).

In the safety population (N=25), ramucirumab dose adjustments included 9 patients (36%) with ≥1 dose reductions, 14 patients (56%) with ≥1 dose delays, and 4 patients (16%) with ≥1 dose omissions (dose withheld) (Supplementary Table S1). Dose modifications for osimertinib included 3 patients (12%) with ≥1 dose reduction and 7 patients (28%) with ≥1 dose omission. AEs were the most common reason for both ramucirumab and osimertinib dose modifications (Supplementary Table S1).

Safety

During phase 1a, no DLTs or unexpected safety signals were observed. All patients in the dose-finding (n=3; 100%) and dose-expansion (n=22; 100%) portions of the study experienced ≥1 TRAE (Table 2). Across all patients, the most common TRAEs were hypertension (any grade n=12, 48%; ≥Grade 3 n=2, 8%), diarrhea (any grade n=9, 36%; ≥Grade 3 n=0), stomatitis (any grade n=6, 24%; ≥Grade 3 n=0), and platelet count decreased (any grade n=6, 24%; ≥Grade 3 n=4, 16%; Table 2). Grade 3 or higher TRAEs were reported in 5 of 15 (33%) patients without CNS metastases and 2 of 10 (20%) patients with CNS metastases (Table 2). A full listing of TRAEs is shown in Supplementary Table S2.

Table 2.

Summary of Adverse Events

	No CNS Metastases N=15		CNS Metastases N=10		All patients N=25
n (%)a	TEAE	TRAEb	TEAE	TRAEb	TEAE	TRAEb
Any grade AE	15 (100)	15 (100)	10 (100)	10 (100)	25 (100)	25 (100)
≥Grade 3 AE	10 (67)	5 (33)	6 (60)	2 (20)	16 (64)	7 (28)
SAE	5 (33)	0 (0)	4 (40)	1 (10)	9 (36)	1 (4)
AE leading to study discontinuation	1 (7)	0 (0)	1 (10)	1 (10)	2 (8)	1 (4)
AE leading to death on treatment c	1 (7)	0 (0)	0 (0)	0 (0)	1 (4)	0 (0)
AE leading to death within 30 days of discontinuing study treatment c	0 (0)	0 (0)	1 (10)	1 (10)	1 (4)	1 (4)
TRAEs in ≥10% all patients by preferred term d
	Any	≥Grade 3	Any	≥Grade 3	Any	≥Grade 3
Hypertension	4 (47)	2 (13)	5 (50)	0 (0)	12 (48)	2 (8)
Diarrhoea	6 (40)	0 (0)	3 (30)	0 (0)	9 (36)	0 (0)
Stomatitis	3 (20)	0 (0)	3 (30)	0 (0)	6 (24)	0 (0)
Platelet count decreased	4 (27)	2 (13)	2 (20)	2 (20)	6 (24)	4 (16)
Rash	4 (27)	0 (0)	1 (10)	0 (0)	5 (20)	0 (0)
Proteinuria	3 (20)	0 (0)	2 (20)	0 (0)	5 (20)	0 (0)
Pruritis	3 (20)	0 (0)	1 (10)	0 (0)	4 (16)	0 (0)
Gingival bleeding	3 (20)	0 (0)	1 (10)	0 (0)	4 (16)	0 (0)
Petechiae	3 (20)	0 (0)	0 (0)	0 (0)	3 (12)	0 (0)
Thrombocytopenia	3 (20)	0 (0)	0 (0)	0 (0)	3 (12)	0 (0)
Asthenia	1 (7)	0 (0)	2 (20)	0 (0)	3 (12)	0 (0)
Fatigue	3 (20)	0 (0)	0 (0)	0 (0)	3 (12)	0 (0)
Edema peripheral	2 (13)	0 (0)	1 (10)	0 (0)	3 (12)	0 (0)
Paronychia	2 (13)	0 (0)	1 (10)	0 (0)	3 (12)	0 (0)
Infusion-related reaction	3 (20)	0 (0)	0 (0)	0 (0)	3 (12)	0 (0)
Neutrophil count decreased	1 (7)	0 (0)	2 (20)	1 (10)	3 (12)	1 (4)
Epitaxis	3 (20)	0 (0)	0 (0)	0 (0)	3 (12)	0 (0)

^aPatients may be counted in more than one category.

^bAEs considered related to study treatment as judged by the investigator.

^cDeaths are also included as SAEs and discontinuations due to AEs.

^dShown by Medical Dictionary for Regulatory Activities preferred terms. Full listing of TRAEs are in Supplementary Table S2.

AE, adverse event; CNS, central nervous system; N, number of patients in population; n, number of patients in specified category; SAE, serious AE; TEAE, treatment-emergent AE; TRAE, treatment-related AE

Overall, SAEs were reported in 9 (36%) patients, 5 (33%) without CNS metastasis and 4 (40%) with CNS metastases (Table 2). One SAE of Grade 2 diverticulitis (33%) was reported in the dose-finding portion of the study, which was unrelated to study treatment. Across all patients, the most commonly reported SAEs were pneumonia (n=2; 8%) and pyrexia (n=3; 12%), which were deemed unrelated to study treatment (Supplementary Table S3). A total of 12 (48%) deaths were reported; 1 (4%) while patients were on study treatment, 6 (24%) within 30 days after discontinuing study treatment, and 5 (20%) >30 days after discontinuing study treatment (Supplementary Table S4). The majority of the 12 deaths were due to lung cancer (n=9; 75%) and 3 (25%) deaths were due to AEs. Of these, one death due to an SAE was deemed possibly related to treatment: a 75-year-old patient with CNS metastases died following Grade 3 congestive heart failure and subsequent Grade 5 subdural hemorrhage, unrelated to CNS metastasis per the investigator, approximately 7 weeks after the last dose of ramucirumab. Of note, the mean elimination half-life for ramucirumab is 14 days (43). The other 2 deaths were due to SAEs (pulmonary edema and cardiac arrest), deemed by investigators to be unrelated to study treatment.

Known AESIs for ramucirumab are tabulated in Supplementary Table S4. Overall, 21 patients (84%) experienced one or more AESI, and 9 patients (36%) experienced ≥Grade 3 AESIs. The most common AESIs were hypertension (any grade n=15, 60%; ≥Grade 3 n=4, 16%), bleeding/hemorrhage events (any grade n=10, 40%; ≥Grade 3 n=1, 4%), and liver injury/liver failure (any grade n=8, 32%; ≥Grade 3 n=1, 4%). As discussed above, deaths resulted from Grade 5 AESIs of subdural hemorrhage and Grade 5 pulmonary edema.

Preliminary efficacy

Confirmed best response based on tumor burden is depicted in Figure 1A. Tumor response over duration of treatment is shown in Figure 1B. The confirmed ORR was 76% (19/25 patients), comprising 1 CR (4%; 90% CI: 0-18) and 18 PR (72%; 90% CI: 54-86). SD was observed in 4 patients (16%; 90% CI: 6-33). In all patients, the median DOR was 13.4 months (90% CI: 9.6-21.2). ORR was 87% (90% CI: 64-98) in patients without CNS metastases and 60% (90% CI: 30-85) in patients with CNS metastases. DCR in patients without CNS metastases was 87% (90% CI: 64-98) compared to 100% (90% CI: 74-100) in patients with CNS metastases.

Figure 1.

A. Confirmed best response based on tumor burden. Investigator-assessed best percentage change in tumor size from baseline is shown for each patient whose disease was assessable by RECIST 1.1 criteria. Patients (x-axis) are color-coded according to best overall response. B. Tumor response over time in treated patients. Tumor response over duration on treatment (A) and percent change in tumor size from baseline over analysis time (B) are shown for each patient, color-coded by best overall response. C. Confirmed Best Overall Systemic Response. CI, confidence interval; CNS, central nervous system; CR, complete response; N, number of patients in population; n, number of patients in specified category; NE, non-evaluable; PD, progressive disease; PR, partial response; SD, stable disease. Response criteria were from RECIST 1.1 and were investigator-assessed. Confidence intervals are based on the Clopper-Pearson method. ^aOne patient did not have post baseline tumor assessment.

Intracranial tumor response for patients with CNS metastasis at baseline is summarized in Supplementary Table S5. CNS activity was observed regardless of prior radiotherapy. Only 1 patient with CNS metastasis had measurable CNS lesions, and this patient exhibited tumor shrinkage of 24% (CNS SD) as best response. The other 9 patients with CNS metastasis had nonmeasurable lesions; of these, 1 had a CNS CR whereas his systemic best response was SD. The remaining patients had CNS non-CR/non-PD.

Median PFS for all patients was 11.0 months (90% CI: 5.5-19.3). The estimated PFS rates at 6, 12, and 24 months were 67%, 50%, and 20%, respectively (Figure 2). Patients who did not have CNS metastases at baseline had a numerically greater median PFS (14.7 months; 90% CI: 5.3-not reached) than that of patients with CNS metastases (10.9 months; 90% CI: 3.5-13.8; Figure 2) although statistical comparisons were not performed.

Figure 2. Progression-free survival.

Data are shown for A) all patients; and B) baseline CNS metastasis categories. The curves and medians (90% CI) were estimated using the Kaplan-Meier method. --, not available; CI, confidence interval; CNS, central nervous system; N, number of patients in population; n, number of patients in specified category; PFS, progression-free survival.

Median OS was not reached at the time of data cut-off. The 6-month, 12-month, and 24-month OS rates for all patients were 84%, 76%, and 52%, respectively (Supplementary Figure S2). The 6-month, 12-month, and 24-month OS rates were numerically lower for patients with baseline CNS metastasis (70%, 60%, and 30%, respectively) compared with patients without baseline CNS metastasis (93%, 87%, and 67%, respectively; Supplementary Figure S2; statistical comparisons not made).

Pharmacokinetics

Ramucirumab serum concentrations were available in 25 patients receiving treatment. Ramucirumab trough and peak concentrations are summarized in Supplementary Table S6. Accumulation was observed between Cycles 2 and 7 in all patients, with the geometric mean of trough sample concentrations more than doubled at Cycle 7 compared with Cycle 2. Moderate variability was observed for trough concentrations (geometric percent coefficient of variation [CV%] ranging from 27% to 56%). End-of-infusion concentrations on Cycle 1 Day 1 had high variability with a geometric mean of 186 μg/ml and a geometric CV% of 76%.

Exploratory Biomarker Analyses

All twenty-five patients were enrolled per protocol to have local test results showing tissue EGFR T790M positivity, in addition to EGFR Exon 19 deletion, or Exon 21 L858R. Fourteen patients had detectable and 4 patients had undetectable EGFR T790M in ctDNA at baseline. Loss of detectable T790M in plasma in the on-treatment sample was observed in all 14 patients, and the 4 patients with undetectable plasma T790M at baseline remained undetectable on-treatment (Figure 3A). Sixteen patients had detectable and two patients had undetectable EGFR Exon 19 deletion or Exon 21 L858R mutation in plasma ctDNA at baseline. In the on-treatment sample, loss of detectable EGFR Exon 19 deletion or Exon 21 L858R mutation was observed in patients with PR only, whereas retention of EGFR Exon 19 deletion or Exon 21 L858R mutation was observed in patients with PR or SD as best objective response (Figure 3B). Patients with loss of EGFR Exon 19 deletion or L858R mutation on treatment appeared to have longer PFS than patients with retention of these mutations on treatment (median PFS 14.7 months vs 5.5 months) (Figure 4). Two patients with EGFR activating mutations undetectable in ctDNA at baseline and on-treatment appeared to have prolonged PFS as well (22.0 months and 24.9 months). The subgroups of patients with loss or retention of on-treatment EGFR activating mutations was also balanced in terms of baseline characteristics being EGFR Exon 19 deletion or L858R and with or without CNS metastasis. Four patients with at least one genetic alteration detectable at both baseline and post progression ctDNA had emergent alterations post progression (Patient 1, EGFR: amplification [amplification]; KRAS: amplification [aneuploidy]; MET: amplification [aneuploidy]; MTOR: R769H, Patient 2, ARAF: I478I; EGFR: amplification [amplification], Patient 3, EGFR: C797S; MET; amplification [focal], and Patient 4, CCND2: R86S).

Figure 3.

A. T790M (Detectable vs. Undetectable on Y axis) in circulating tumor DNA over time (3 time points, along X axis) and correlation with best overall response (color coded) and progression-free survival (ordered along Z axis by descending PFS). B. EGFR- Exon 19 deletion or Exon 21 L858R mutation in circulating tumor DNA similarly presented over time and correlation with best overall response and progression-free survival. Plasma samples were collected for assessment of circulating tumor DNA at baseline, during treatment (Cycle 4 Day 1 or Cycle 7 Day 1), and post progression (30-day follow-up). Genetic alterations were assessed by Guardant 360^® next-generation sequencing. Patients are color-coded according to best overall response. BOR, best overall response; CR, complete response; n, number of subjects in the specified category; NE, non-evaluable; PD, progressive disease; PFS, progression-free survival; PR, partial response; SD, stable disease.

Figure 4. Kaplan-Meier plot of progression-free survival by loss or retention of the EGFR- Exon 19 deletion or Exon 21 L858R mutation in circulating tumor DNA.

The curves and medians (95% CI) were estimated using the Kaplan-Meier method. Loss or retention of the EGFR activating mutation is defined as being undetectable or detectable, respectively, in on-treatment ctDNA samples, as only samples detectable for EGFR activating mutations at baseline are included for this analysis. Plasma samples were collected for assessment of circulating tumor DNA at baseline and during treatment (Cycle 4 Day 1 or Cycle 7 Day 1). Note: In the subgroup of 8 patients with on-treatment loss of EGFR activating mutations, 6 had Exon 19 deletion, and 2 had L858R at baseline, whereas in the subgroup of 8 patients with retained EGFR activating mutations on treatment, 5 had Exon 19 deletion, and 3 had L858R at baseline. In addition, there were 4 patients with CNS metastasis and 4 patients without in each subgroups of on-treatment loss or retained EGFR activating mutations. Responder: CR or PR as BOR. Non-responder: SD as BOR. BOR, best overall response; CR, complete response; PR, partial response; SD, stable disease.

Discussion

This phase 1 study evaluated the safety, pharmacokinetics, and preliminary efficacy of ramucirumab administered in combination with osimertinib in patients with advanced EGFR-mutant NSCLC who had progressed after initial EGFR TKI therapy but were naïve to third-generation EGFR TKIs. In the dose-finding portion of the study, no DLTs were observed for the combination therapy with full doses of both agents. Across both portions of the study, the safety profile for the combination therapy was consistent with that seen with monotherapy for each drug (9,23), with no unexpected safety signals and no additive toxicities reported. All patients had at least one TRAE, but serious TRAEs or TRAEs leading to death or discontinuation were infrequent (Table 2). The most common Grade 3 or higher TRAEs were hypertension and decreased platelet count, with only 1 (4%) patient discontinuing ramucirumab due to a ≥Grade 3 TRAE (congestive heart failure). Based on these findings, ramucirumab at a dose level of 10 mg/kg IV every 2 weeks can be administered safely in combination with daily oral osimertinib 80 mg in patients with advanced NSCLC. In addition, the current pharmacokinetic results are consistent with known ramucirumab pharmacokinetic characteristics (41,44,45), with a stable clearance profile indicative of saturation of the VEGFR2-mediated clearance pathway (44). These findings indicate that co-administration with osimertinib is unlikely to affect ramucirumab pharmacokinetics.

Osimertinib was initially approved by the FDA in the United States for the treatment of patients with metastatic T790M-positive EGFR-mutant NSCLC (8,10,29). In a recent pooled analysis of two single-arm, open-label phase 2 studies in patients with EGFR mutant-positive advanced NSCLC who had progressed after initial EGFR TKI therapy and were found to be T790M-positive, ORR for osimertinib was 66%, and median DOR and median PFS were 12.3 and 9.9 months, respectively (9). In the current study, with the addition of ramucirumab to osimertinib, the ORR was 76%, with a median DOR of 13.4 months and median PFS of 11.0 months; systemic disease control was seen in all patients except one patient with PD and one patient without post baseline tumor assessment. As osimertinib is now largely used in the first-line setting, the combination of osimertinib and ramucirumab is being tested prospectively as first-line treatment in a randomized phase 2 study to determine whether it improves the efficacy of osimertinib monotherapy (NCT03909334), including patients with asymptomatic CNS metastasis.

Planned exploratory analyses examined the safety and efficacy of ramucirumab plus osimertinib in patients with and without CNS metastasis. CNS metastasis is common in patients with EGFR-mutant positive advanced NSCLC and is associated with a poor prognosis and quality of life (46). In the current analysis, 10 patients (40%) had CNS metastasis at baseline, including both patients with (n=7) and without (n=3) prior radiotherapy. A pooled analysis in patients with T790M-positive NSCLC who had progressed after prior EGFR TKI therapy reported numerically different efficacy for osimertinib in patients with and without CNS metastasis (systemic ORR, 59% and 70%; PFS, 8.2 and 12.4 months, respectively) (9). Similarly, in the current study, systemic disease control was observed in patients treated with ramucirumab plus osimertinib regardless of baseline CNS metastasis status (systemic ORR 60% and 87%; DCR 100% and 87%, for patients with and without baseline CNS metastasis, respectively), and the intracranial DCR for those with CNS metastasis at baseline was high (CNS DCR 100%). In keeping with the published literature showing poorer survival of patients with NSCLC and CNS metastasis (46), patients with CNS metastasis at baseline receiving ramucirumab plus osimertinib demonstrated a shorter median PFS and had lower landmark OS rates than patients without baseline CNS metastasis (e.g., median PFS 10.9 and 14.7 months, respectively; 24-month OS rate, 30% and 67%, respectively), although statistical comparisons were not made. To date, the CNS efficacy of ramucirumab as a monotherapy or in combination with other therapies has not been well studied, although the use of ramucirumab in NSCLC patients with treated CNS metastasis, in combination with docetaxel, has been determined to be safe based on a randomized phase 3 study (23). For example, patients with brain metastasis were excluded from the recent phase 3 study examining ramucirumab in combination with the EGFR TKI erlotinib in NSCLC (17), and the current study is the first study of ramucirumab that enrolled patients with untreated CNS metastasis. The current results indicate that ramucirumab plus osimertinib is well tolerated in NSCLC patients with or without CNS metastasis. These results are consistent with prior demonstrations of the CNS efficacy of osimertinib (14,29) and biologic VEGF inhibitors (31-33,35,37,38) in patients with NSCLC.

The loss of T790M on treatment has been reported with the use of osimertinib (47,48); however, timing of the T790M loss, either on treatment or post progression, would suggest whether loss of T790M represents response to treatment or a mechanism of resistance to therapy. Our preliminary results demonstrate that T790M is lost early on treatment, suggesting the loss of T790M is not related to mechanism of resistance. Undetectable EGFR Exon 19 deletion or Exon 21 L858R in ctDNA at baseline despite positivity in tissue and loss of EGFR Exon 19 deletion or Exon 21 L858R in ctDNA on-treatment have been explored as a predictor of response and are associated with longer PFS. This finding was also observed in another study exploring ramucirumab plus erlotinib in Japanese patients with first-line EGFR-mutated NSCLC and in other studies of osimertinib monotherapy (49,50). This correlation warrants further validation, as it suggests EGFR ctDNA could be a biomarker to help identify patients who may not have durable responses to therapy and may benefit from escalation of care.

Although the single-arm design and small sample size of this study limit the conclusions that can be drawn, the current findings are promising and warrant additional study. In this phase 1 study, ramucirumab plus osimertinib demonstrated encouraging antitumor activity in T790M-positive EGFR-mutant advanced NSCLC. In addition, the safety profile was consistent with monotherapy for each drug, with no clear additive toxicities, supporting ramucirumab plus osimertinib as a safe and tolerable combination treatment regimen in this patient population. As VEGF inhibitors and osimertinib both have excellent CNS activity, there is interest in using the combination for patients with CNS involvement who historically have poorer outcomes with the standard therapy. In addition, retention of the sensitizing EGFR mutation in ctDNA on treatment correlates with worse progression-free survival on EGFR TKIs, including osimertinib, as monotherapy or in combination with anti-VEGF therapy, suggesting the subgroup of patients with retention of EGFR ctDNA may benefit from escalation of care. Indeed, a prospective randomized trial (NCT03909334) is ongoing to determine the effectiveness of combination therapy with anti-VEGF therapy by comparing osimertinib plus ramucirumab to osimertinib alone. These findings, together with the recent report of the PFS benefit of ramucirumab plus erlotinib in patients with untreated EGFR-mutated metastatic NSCLC (17), indicate that the dual targeting of EGFR and VEGFR pathways may be a promising new treatment strategy for EGFR-mutant advanced NSCLC.