Purpose:

Osimertinib is an effective therapy in EGFR-mutant non–small cell lung cancer (NSCLC), but resistance invariably develops. Navitoclax is an oral inhibitor of BCL-2/BCL-xL that has exhibited synergy with osimertinib in preclinical models of EGFR-mutant NSCLC. In hematologic malignancies, BCL-2 family inhibitors in combination therapy effectively increase cellular apoptosis and decrease drug resistance.

Patients and Methods:

This single-arm phase Ib study evaluated safety, tolerability, and feasibility of osimertinib and navitoclax, including dose expansion in T790M-positive patients at the recommended phase II dose (RP2D). Eligible patients had advanced EGFR-mutant NSCLC with prior tyrosine kinase inhibitor exposure. Five dose levels were planned with osimertinib from 40 to 80 mg orally daily and navitoclax from 150 to 325 mg orally daily.

Results:

A total of 27 patients were enrolled (18 in the dose-escalation cohort and nine in the dose-expansion cohort): median age 65, 67% female, 48% exon 19 del, and 37% L858R, median one prior line of therapy. The most common adverse events were lymphopenia (37%), fatigue (22%), nausea (22%), and thrombocytopenia (37%). No dose-limiting toxicities were seen in dose-escalation cohort; osimertinib 80 mg, navitoclax 150 mg was chosen as the RP2D. Most patients (78%) received >95% of planned doses through three cycles. In expansion cohort, objective response rate was 100% and median progression-free survival was 16.8 months. A proapoptotic effect from navitoclax was demonstrated by early-onset thrombocytopenia.

Conclusions:

Oral combination therapy with navitoclax and osimertinib was safe and feasible at RP2D with clinical efficacy. Early thrombocytopenia was common, supporting an target engagement by navitoclax. Further study of BCL-2/BCL-xL inhibition to enhance osimertinib activity is warranted.

This article is featured in Highlights of This Issue, p. 1583

Translational Relevance

EGFR-mutant non–small cell lung cancer (NSCLC) represents a unique subset of lung cancers with sensitivity to EGFR-targeted therapy. Although initial responses are often clinically significant, they are not durable due to drug resistance. This trial evaluated utilization of navitoclax, an oral BCL-2/BCL-xL inhibitor, with osimertinib, a third-generation EGFR tyrosine kinase inhibitor (TKI), in EGFR-mutant NSCLC. This combination is relevant to ongoing studies of proapoptotic agents and distinct from many osimertinib combinations as it is intended to increase the effectiveness of osimertinib in a TKI-sensitive population. In addition, the trial was one of very few oral combinations being studied for this purpose. Our study demonstrates the tolerability and feasibility of this combination as well as compelling efficacy in T790M-positive NSCLC, with durable responses and complete clearance of circulating tumor DNA. The trial closed to enrollment early when osimertinib became a first-line agent, but our data now are being used to advance a first-line combination study.

Highly active oral targeted therapies have transformed the care of non–small cell lung cancer (NSCLC), with more than a dozen targeted therapies now approved as single agents for molecularly defined subsets of advanced NSCLC. Although these drugs are highly effective and many have been shown to be superior first-line therapies in randomized trials, patients inevitably develop drug resistance at which point treatment options are more limited. Lung cancers harboring EGFR mutations represent the most common NSCLC genotype globally and are routinely treated with osimertinib (AZD9291), a third-generation EGFR inhibitor, either in the first-line setting or following development of drug resistance due to an EGFR T790M mutation (1). Given its activity and favorable toxicity profile, combinations of osimertinib with other targeted therapies are of clinical interest to improve outcomes for patients with advanced EGFR-mutant NSCLC.

Combination therapy with proapoptotic agents has emerged as a compelling strategy for increasing the activity of cancer therapeutics. Two leading agents are venetoclax (ABT-199/GDC-0199), a selective BCL-2 inhibitor approved for the treatment of hematologic malignancies [chronic lymphocytic leukemia (CLL) and acute myeloid leukemia], and navitoclax (ABT-263), an inhibitor of BCL-xL, BCL-2, and other BCL-2 family proteins. In contrast to other known oncoproteins, BCL-2 does not stimulate cellular proliferation, but rather inhibits programmed cell death by protecting cells from a wide variety of proapoptotic stimuli, including cytokine withdrawal, irradiation, cytotoxic drugs, heat, and deregulated oncogenes (2–4). In hematologic malignancies, BCL inhibition has demonstrated significant synergy with targeted therapies, including with ibrutinib and rituximab. Common toxicities include cytopenias, particularly neutropenia and thrombocytopenia, and gastrointestinal side effects, including diarrhea and abdominal pain (5–7).

In EGFR-mutant lung cancer, preclinical studies demonstrated that models with a low level of the proapoptotic protein BIM had a suboptimal response to EGFR tyrosine kinase inhibitor (TKI; ref. 8). Moreover, lung cancer cell lines with TKI resistance, in particular those harboring T790M after prior TKI exposure, demonstrated reduced apoptotic response to EGFR inhibition over time. In this setting, the addition of navitoclax demonstrated increased apoptotic activity in combination with a third-generation TKI similar to osimertinib (9). This preclinical works supports the hypothesis that impairing the activity of antiapoptotic proteins could shift this balance in favor of apoptosis and achieve more dramatic tumor response. It is therefore hypothesized that the addition of navitoclax to osimertinib in T790M-positive lung cancers could improve the apoptotic response, resulting in deeper and more durable regressions. To investigate this hypothesis, we performed a phase Ib trial of osimertinib and navitoclax in pretreated EGFR-mutant NSCLC.

Patients

Between March 2016 and April 2019, we enrolled 27 patients to a single-arm, multiinstitution phase I trial. This study was approved by the institutional review board of all the participating centers, and this trial was conducted in accordance with Good Clinical Practice guidelines and the provisions of the Declaration of Helsinki. Patients were required to provide informed written consent before any study-related procedures. This protocol is also registered with clinicaltrials.gov (identifier NCT02520778). This first-in-human combination study enrolled patients with previously treated advanced NSCLC harboring an activating EGFR mutation who had progressed on a prior EGFR-directed TKI. In the dose-escalation portion of the study, patients were eligible regardless of the specific resistance mechanism to prior EGFR TKI treatment. Dose expansion was limited to patients whose tumor had an EGFR T790M mutation based on local testing and were osimertinib naive. Fresh or archival tissue submission was optional in the dose-escalation cohort, but was required for those enrolled to the dose-expansion portion of the study. The study was developed prior to the adoption of osimertinib as first-line therapy, thus treatment-naïve patients were not allowed. Patients with brain metastases could be enrolled after completing local treatment and could not be on corticosteroids. All patients were required to have measurable disease by RECIST 1.1 and Eastern Cooperative Oncology Group performance status 0–1 (10). Women of child-bearing age were required to have a negative serum pregnancy test within 7 days before enrollment. Adequate organ function and bone marrow reserve was required [absolute neutrophil count > 1,500, platelets > 100,000, total bilirubin ≤ 1.5 mg/dL, alanine aminotransferase/aspartate aminotransferase ≤ 3 times the upper limit of normal, and creatinine ≤2 mg/dL (or creatinine clearance ≥ 50 mL/minute)].

Exclusion criteria included a significant cardiovascular event within 6 months (myocardial infarct, thrombotic or thromboembolic event), underlying bleeding disorders, history of a clinically significant bleeding event or nonchemotherapy induced thrombocytopenic-associated bleeding. Uncontrolled brain metastases or leptomeningeal disease was not permitted. Patients receiving anticoagulation or antiplatelet therapy were excluded because of risk of thrombocytopenia with navitoclax. Excluded agents included heparin or low-molecular-weight heparin, warfarin, clopidogrel, ibuprofen and other NSAIDS, tirofiban, and other anticoagulants, drugs, or herbal supplements that affect platelet function.

There was no limit on prior therapy, although prior treatment with a third-generation T790M-directed TKI was only permitted for patients enrolled on the dose-escalation portion of trial. A 7-day washout was required between last dose of EGFR TKI and study enrollment. HIV-positive patients on antiretroviral therapy were not permitted because of the possibility of drug interactions.

Study design/treatment plan

The study was designed as a single-arm phase Ib study that included dose escalation of both osimertinib and navitoclax, conducted with a standard 3+3 design, followed by expansion at the recommended phase II dose (RP2D). Osimertinib and navitoclax were supplied by the Pharmaceutical Management Branch of the Cancer Therapy Evaluation Program (CTEP), NCI under a collaborative agreement with AstraZeneca and AbbVie. In the dose-escalation cohort, cycle 1 started with a 3-day lead-in of navitoclax only, prior to starting osimertinib on cycle 1 day 4 for pharmacokinetic analysis of single-agent navitoclax prior to combination therapy. Osimertinib was initially dosed at 40 mg daily, an active dose, and then increased to 80 mg daily in dose level 2 (DL2) and subsequent DLs. Navitoclax was initially dosed at 150 mg daily, below the single-agent MTD of 325 mg daily, and then increased to 200 mg daily and higher starting from DL3. At doses above 150 mg, a navitoclax lead-in dose of 150 mg daily for 7 days was included prior to escalation to permit stabilization of platelet levels, which are known to drop during this lead-in period (11, 12). In the dose-expansion cohort, both agents started together on cycle 1 day 1.

Dose-limiting toxicity (DLT) was assessed during cycle 1 in patients who had received at least 75% of the planned doses in cycle 1 (unless held due to DLT). DLT was defined ≥ grade 3 nonhematologic toxicity, except nausea, vomiting, or diarrhea resolving to at least grade 1 within 48 hours. Grade 3 rash was considered a DLT only if not improved within 72 hours with maximal medical management. Additional DLTs included febrile neutropenia, grade 4 neutropenia, anemia, or thrombocytopenia; thrombocytopenic bleeding, pneumonitis ≥ grade 2, or delay in starting cycle 2 of ≥ 14 days due to toxicity of any grade related to one or more protocol drugs. Dose reductions were made independently for each drug based on attribution. If toxicity resulted in one study drug discontinuation, the other drug was permitted to continue. All toxicities were assessed using Common Terminology Criteria for Adverse Events, version 4.03. Toxicity assessments were completed through October 2019.

Analysis plan

The primary endpoints in this phase Ib trial were to assess toxicity during dose escalation and feasibility during dose expansion. Feasibility was specifically assessed as ability for patients to tolerate combination dosing (osimertinib and navitoclax) for at least 12 weeks (three cycles). All patients who started therapy were included in the toxicity assessment with toxicities reported through data lock in October 2019. Data were initially locked in October 2019; additional clinical outcomes data, including survival, were collected through June 2020.

Measurable disease was required for study enrollment. Baseline computerized tomography scans were done within 4 weeks of starting study treatment in all patients and repeated after every two cycles. RECIST 1.1 was used for assessment of tumor response. All responding patients were required to have their response confirmed 4 to 6 weeks after the first documentation of response. Progression-free survival (PFS) was calculated from the date of the cycle 1 of study treatment.

Planned sample size included up to 30 patients in the dose-escalation portion and 20 patients in the dose-expansion cohort. The dose expansion at RP2D was planned to assess a response rate as compared with historical controls for T790M-positive patients.

Correlative analysis

Fresh or archival tissue was required from all enrolled patients in the dose-expansion cohort for central T790M testing and next-generation sequencing using Oncopanel at Dana-Farber Cancer Institute (Boston, MA; ref. 13). Tissue submission was optional for those with prior local T790M testing results in the dose-escalation cohort. Analysis of circulating tumor DNA (ctDNA) using droplet digital PCR (ddPCR) was performed at the Belfer Center for Applied Cancer Science at Dana-Farber Cancer Institute (Boston, MA), as described previously (14). Each specimen was tested separately for EGFR T790M and the known sensitizing mutation (L858R or exon 19 deletion). Plasma ctDNA samples were collected as baseline, day 1 of each cycle, and at the end-of-study visit. Patients who had no detectable EGFR mutations in plasma at baseline were excluded from further plasma analysis.

Because osimertinib induces CYP3A4 and navitoclax is a CYP3A4 substrate, enzyme induction may reduce navitoclax plasma concentrations. Therefore, pharmacokinetic studies were performed to assess for this possible drug–drug interaction (15, 16). Samples for analysis of navitoclax were collected on day 3 of cycle 1 after a 3-day lead-in of single-agent navitoclax prior to dosing and at 1, 2, 3, 4, 6, and 8 hours after dosing and again on cycle 2, day 1 after 25 days of combination therapy. Samples for osimertinib and active metabolites were obtained at the same time as navitoclax sampling in cycle 2. Navitoclax, osimertinib, and active metabolites AZ5104, AZ7550 were measured by validated LC/MS-MS assays and Cmax and AUC were calculated with noncompartmental analyses using Phoenix 64 WinNonlin and dose adjusted (11, 17).

Patient characteristics

A total of 27 patients with a median age of 65 years (range, 40–83 years) were enrolled on trial. Most patients were female (67%), with 48% exon 19 del and 37% L858R. Most patients received one prior systemic lung cancer treatment (14 patients, 52%); seven patients received two prior lines of therapy, and six patients had received three or more prior therapies. All patients had received at least one EGFR TKI (24 erlotinib, six afatinib, six osimertinib, one rociletinib), two patients received immunotherapy, two patients received bevacizumab, two patients received investigation TKI therapy (MET inhibitor, MEK inhibitor, and AXL inhibitor), and 10 patients received prior chemotherapy. Nineteen patients had histologic assessment at time of study enrollment; most were adenocarcinoma, except one adenocarcinoma with rhabdoid features, one adenosquamous, one small cell transformation (dose escalation), and three NSCLC NOS. Demographic information is detailed in Table 1.

Table 1.

Patient demographics.

Patients, N 27 
Men, N (%) 9 (33) 
Women, N (%) 18 (67) 
Age in years, median (min–max) 65 (40–83) 
Prior systemic therapy, N (%) 
Erlotinib 24 
Afatinib 
Osimertinib 
Immunotherapy 
Chemotherapy 10 
Bevacizumab 
Other clinical trial therapy 
EGFR mutation 
L858R 10 (37) 
Exon 19 del 13 (48) 
Other—L861Q, G719S, S768I
 
4 (15) 
T790M 15 (55.5%) 
Patients, N 27 
Men, N (%) 9 (33) 
Women, N (%) 18 (67) 
Age in years, median (min–max) 65 (40–83) 
Prior systemic therapy, N (%) 
Erlotinib 24 
Afatinib 
Osimertinib 
Immunotherapy 
Chemotherapy 10 
Bevacizumab 
Other clinical trial therapy 
EGFR mutation 
L858R 10 (37) 
Exon 19 del 13 (48) 
Other—L861Q, G719S, S768I
 
4 (15) 
T790M 15 (55.5%) 

Twelve patients, five of 18 from the dose-escalation and seven of nine from the dose-expansion cohorts, had adequate tissue submitted for central tumor sequencing. All 12 had confirmed EGFR mutations (six exon 19 deletion, four L858R, one L861Q, and one with both G719S and S768I). Eight (67%) had EGFR T790M on central testing. An additional six patients had T790M based on local testing only without tissue submitted for central confirmation. Eight of 12 (67%) with central testing had at least one additional oncogene or tumor suppressor gene alteration in addition to mutation(s) in EGFR. Seven of 12 (58%) had concomitant TP53 mutations, and one patient had both TP53 and RB1 alterations. Three of 12 (25%) had CTNNB1 mutations, two of 12 (17%) had PI3KCA mutations, and one of 12 (8%) had APC or CDKN2A mutations.

Safety and feasibility

Eighteen patients were treated during the dose-escalation portion of the study; nine patients were treated during dose expansion (Supplementary Table S1). In the dose-escalation cohort, four patients were enrolled in DL1, seven at DL2, and seven at DL3. One patient at each DL was nonevaluable for safety and feasibility due to either disease progression (n = 1) or poor compliance (n = 2). Among 15 DLT-evaluable patients, no DLTs were seen; however, three of seven patients (43%) in DL3 (osimertinib 80 mg + navitoclax 200 mg) required dose reductions during cycle 1 suggesting dose expansion at DL3 would not be well tolerated. For DLs 1 and 2, three patients had navitoclax dose reductions and no patients required osimertinib dose reductions during cycles 1 or 2. In the dose-expansion cohort, one patient dose reduced both navitoclax and osimeritinib after cycle 1, one patient dose reduced navitoclax after cycle 2, and one patient discontinued navitoclax after cycle 2 due to venous thromboemboli (VTE; Supplementary Table S1). Toxicities requiring dose reduction at DL3 included diarrhea (grade 3), fatigue (grade 3), generalized muscle weakness (grade 3), and abdominal bloating (grade 2).

DL2 (osimertinib 80 mg + navitoclax 150 mg) was selected as the RP2D for further study. In dose expansion, nine patients with EGFR T790M resistance and no prior third-generation TKI were enrolled before study enrollment was discontinued because of slow enrollment and with the approval of osimertinib as first-line therapy. Feasibility of combination dosing over the initial 3 months of therapy was studied in these nine patients. Seven of nine patients (78%) received >95% of planned doses through three cycles (Fig. 1). Two patients developed VTE; one patient developed a pulmonary embolus after cycle 2 and one patient had a deep vein thrombosis after cycle 9. Both patients started anticoagulation and discontinued navitoclax, per protocol, due to the potential for increased bleeding risk, but continued osimertinib on study.

Figure 1.

Feasibility of combination therapy and PFS. Swimmer plot demonstrating PFS for each subject in the expansion phase including duration of each individual therapy. Seven of nine continued navitoclax and nine of nine continued osimertinib until progression. Five of nine patients have ongoing PFS as indicated by arrows.

Figure 1.

Feasibility of combination therapy and PFS. Swimmer plot demonstrating PFS for each subject in the expansion phase including duration of each individual therapy. Seven of nine continued navitoclax and nine of nine continued osimertinib until progression. Five of nine patients have ongoing PFS as indicated by arrows.

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Most toxicities were grade 2; no grade 4 or 5 treatment-related toxicities were observed. The most common treatment-related adverse events at any DL were fatigue (26% grade 2–3), leukopenia/lymphopenia (37% grade 2–3), thrombocytopenia (37% grade 2–3), diarrhea (33% grade 2–3), and nausea (22% grade 2). Grade 3 toxicities included cytopenias (neutropenia 3.7%, lymphopenia 11%, thrombocytopenia 11%), diarrhea (18.5%), electrolyte imbalances (hyponatremia 3.7%, hypocalcemia 3.7%, hypophosphatemia 3.7%), fatigue (3.7%), muscle weakness (3.7%), and QT prolongation (3.7%). Thrombocytopenia was not associated with bleeding events. The most common reason for study discontinuation was progressive disease; three patients discontinued navitoclax due to initiation of anticoagulation. Dose reductions for navitoclax were required for hypokalemia, fatigue, thrombocytopenia, diarrhea, and intolerable bloating (grade 2). Treatment-related toxicities of at least grade 2 are summarized in Table 2, grade 1 toxicities are included in Supplementary Table S2.

Table 2.

Treatment-related grade ≥ 2 adverse events.

ToxicityGrade 2 N (%)Grade 3 N (%)
Neutropenia 2 (7.4) 1 (3.7) 
Thrombocytopenia 7 (25.9) 3 (11.1) 
Leukopenia/lymphopenia 7 (25.9) 3 (11.1) 
White blood cell decreased 6 (22.2) 1 (3.7) 
Anemia 1 (3.7)  
Diarrhea 4 (14.8) 5 (18.5) 
Nausea 6 (22.2)  
Vomiting 2 (7.4)  
Flatulence 1 (3.7)  
Gastroesophageal reflux disease 1 (3.7)  
Dysgeusia 1 (3.7)  
Dyspepsia 2 (7.4)  
Alanine aminotransferase increase 1 (3.7)  
Hypoalbuminemia 1 (3.7)  
Hyponatremia  1 (3.7) 
Hypocalcemia  1 (3.7) 
Hypophosphatemia  1 (3.7) 
Allergic reaction 1 (3.7)  
Rash maculopapular 1 (3.7)  
Rash pustular 1 (3.7)  
Dehydration 1 (3.7)  
Dizziness 1 (3.7)  
Dry skin 2 (7.4)  
Paronychia 1 (3.7)  
Electrocardiogram QT corrected interval prolonged  1 (3.7) 
Fatigue 6 (22.2) 1 (3.7) 
Generalized muscle weakness  1 (3.7) 
Pleural effusion 1 (3.7)  
Vaginal hemorrhage 1 (3.7)  
Weight loss 1 (3.7)  
ToxicityGrade 2 N (%)Grade 3 N (%)
Neutropenia 2 (7.4) 1 (3.7) 
Thrombocytopenia 7 (25.9) 3 (11.1) 
Leukopenia/lymphopenia 7 (25.9) 3 (11.1) 
White blood cell decreased 6 (22.2) 1 (3.7) 
Anemia 1 (3.7)  
Diarrhea 4 (14.8) 5 (18.5) 
Nausea 6 (22.2)  
Vomiting 2 (7.4)  
Flatulence 1 (3.7)  
Gastroesophageal reflux disease 1 (3.7)  
Dysgeusia 1 (3.7)  
Dyspepsia 2 (7.4)  
Alanine aminotransferase increase 1 (3.7)  
Hypoalbuminemia 1 (3.7)  
Hyponatremia  1 (3.7) 
Hypocalcemia  1 (3.7) 
Hypophosphatemia  1 (3.7) 
Allergic reaction 1 (3.7)  
Rash maculopapular 1 (3.7)  
Rash pustular 1 (3.7)  
Dehydration 1 (3.7)  
Dizziness 1 (3.7)  
Dry skin 2 (7.4)  
Paronychia 1 (3.7)  
Electrocardiogram QT corrected interval prolonged  1 (3.7) 
Fatigue 6 (22.2) 1 (3.7) 
Generalized muscle weakness  1 (3.7) 
Pleural effusion 1 (3.7)  
Vaginal hemorrhage 1 (3.7)  
Weight loss 1 (3.7)  

Pharmacokinetics and pharmacodynamics

Navitoclax drug levels were studied to confirm active dosing at the levels studied (100–200 mg daily). The plasma concentrations achieved were similar to those observed in prior reports (see Supplementary Materials and Methods; ref. 11). There was no evidence of a clinically significant drug–drug interaction based on pharmacokinetic assessments during cycle 1 (navitoclax alone) and cycle 2 (navitoclax plus osimertinib; see Supplementary Materials and Methods).

Platelet counts were assessed at day 3 after starting navitoclax. All 27 patients (100%) experienced platelet decline at day 3 at all DLs with a median decrease of 70%. Platelet counts recovered within the first 2 weeks of combination therapy with osimertinib and the majority remained stable throughout the duration of therapy (Fig. 2).

Figure 2.

Platelet count trends by DL. Graph of platelet counts from serial complete blood counts collected at baseline, day 3, and then weekly after first dose of navitoclax. Platelet counts demonstrate proapoptotic effect of navitoclax on platelets across a range of doses, including dose level 1 (A), dose level 2 (B), dose level 3 (C), expansion cohort (D).

Figure 2.

Platelet count trends by DL. Graph of platelet counts from serial complete blood counts collected at baseline, day 3, and then weekly after first dose of navitoclax. Platelet counts demonstrate proapoptotic effect of navitoclax on platelets across a range of doses, including dose level 1 (A), dose level 2 (B), dose level 3 (C), expansion cohort (D).

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Efficacy analysis

All 27 patients enrolled on trial were considered evaluable for response. In the dose-escalation cohort (n = 18), partial response was the best response observed in two patients (11%), stable disease in 12 patients (67%), and progressive disease in four patients (22%). Both patients in the dose-escalation cohort with responses were treated on DL3, osimeritinib-naïve, and T790M positive. One patient received first-line erlotinib and the other patient received first-line combination therapy with erlotinib and bevacizumab. No responses were observed in the patients with prior osimertinib treatment. There was no clear correlation between T790M status and response in the dose-escalation cohort (Supplementary Table S1). All patients with prior osimertinib exposure developed disease progression within the first two cycles. In the dose-expansion phase (n = 9), the objective response rate (ORR) was 100%, including one complete response (11%) and eight partial responses (89%; Fig. 3). DLs and best response are also in Supplementary Table S1.

Figure 3.

Tumor response to osimertinib and navitoclax. Waterfall plots of best tumor response as measured by percentage reduction in sum of tumor diameters relative to baseline for patients in the dose-escalation cohort (A) and expansion cohort (B) treated at the RP2D of osimertinib and navitoclax.

Figure 3.

Tumor response to osimertinib and navitoclax. Waterfall plots of best tumor response as measured by percentage reduction in sum of tumor diameters relative to baseline for patients in the dose-escalation cohort (A) and expansion cohort (B) treated at the RP2D of osimertinib and navitoclax.

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At the time of data analysis, 20 patients had progressed, while seven patients remain free from progression. The median PFS was 7.6 months, [95% confidence interval (CI), 1.9–12.6 months] with a 6-month PFS rate of 51.6% (95% CI, 31.6–61.4). For the expansion cohort, median PFS was 16.8 months (95% CI, 3.5–NR; Fig. 1). The 12-month PFS rate was 76.2% (95% CI, 33.2–93.5).

Correlative biomarker studies

ddPCR was performed on plasma ctDNA at baseline and subsequently on day 1 of each cycle starting with cycle 1. Of 27 patients, eight (29.6%) had no detectable EGFR mutations (including exon 19 or L858R) in plasma at baseline; of the remaining 19 patients, 16 had plasma evaluable for ctDNA analysis at multiple time points, including nine in the dose-escalation cohort and seven in the dose-expansion cohort. Plasma ctDNA response was measured as change in allele frequency (AF) of the EGFR driver mutation between baseline and treatment dosing. By cycle 2, 14 patients (87.5%) demonstrated a decrease in plasma ctDNA (del19 and L8585R; ref. 2). In addition, of the 10 patients who had detectable T790M in plasma, 60% demonstrated a decrease in plasma T790M by cycle 2. All seven evaluable patients in the dose-expansion cohort demonstrated a complete ctDNA response with no detectable EGFR mutation after two cycles (Fig. 4).

Figure 4.

ctDNA analyses. A, Scatterplot of baseline EGFR AF. Of 27 patients enrolled, ddPCR detected EGFR exon 19 deletion or L858R driver mutation in 19 patients (70.4%) in pretreatment plasma. Exon 19 deletion was detected in 12 patients (44.4%) and L858R in seven patients (25.9%). Eight patients did not have detectable EGFR mutation by ddPCR. B, Percent change in AF from baseline to cycle 2 in all patients. In the expansion cohort, 100% (7/7) had clearance of detectable EGFR mutation in plasma.

Figure 4.

ctDNA analyses. A, Scatterplot of baseline EGFR AF. Of 27 patients enrolled, ddPCR detected EGFR exon 19 deletion or L858R driver mutation in 19 patients (70.4%) in pretreatment plasma. Exon 19 deletion was detected in 12 patients (44.4%) and L858R in seven patients (25.9%). Eight patients did not have detectable EGFR mutation by ddPCR. B, Percent change in AF from baseline to cycle 2 in all patients. In the expansion cohort, 100% (7/7) had clearance of detectable EGFR mutation in plasma.

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This phase Ib trial of osimertinib and navitoclax demonstrated that combination therapy was feasible with preliminary clinical activity demonstrated in an expansion cohort. Our study evaluated the combination of osimertinib and navitoclax in the setting of acquired resistance to first- or second-generation EGFR TKIs with required presence of T790M in the expansion cohort. In the expansion cohort of T790M-positive patients, the ORR was 100% with one patient achieving a complete response. Most patients in the dose-expansion cohort (7/9, 78%) were able to maintain combination dosing at the RP2D through the first 3 months of therapy, with a median PFS of 16.8 months (12-month PFS rate 76.2%), which compares favorably with the known efficacy of osimertinib in the setting of T790M-positive acquired resistance (18). The clearance of circulating tumor DNA in patients in the expansion cohort also supports the on-target effect of this combination approach.

In addition, dosing at the RP2D of osimertinib 80 mg daily and navitoclax 150 mg daily was well tolerated. Both drugs are known to be associated with thrombocytopenia. Although significant platelet decreases occurred early in the treatment course, no bleeding or other adverse events were associated with severe thrombocytopenia; platelet counts typically recovered and stabilized for the duration of therapy. In fact, the rapid onset of thrombocytopenia on this treatment prior to the introduction of osimertinib is an indication of the intended target engagement of navitoclax, which was seen even at the lower doses used in this combination. Two patients developed thromboemboli in the expansion cohort. One of these patients had a prior history of a provoked lower extremity DVT preceding his cancer diagnosis and was off anticoagulation. These events were not attributed to navitoclax by the investigators and active malignancy along is known to increase the risk of thrombotic events. Given that thrombocytopenia was not prolonged or associated with bleeding events, it may be reasonable to consider inclusion of patients on anticoagulation in future studies.

Osimertinib is typically well tolerated as a single agent and our study demonstrates that overlapping toxicities, such as thrombocytopenia and gastrointestinal adverse events were manageable. In April 2018, after initial design of this study, osimertinib was approved as first-line therapy due to improved PFS compared with erlotinib or gefitinib in the first-line setting (19–21). Osimertinib is now most commonly used as a first-line agent. The safety and feasibility of osimertinib plus navitoclax in this study supports further study of this regimen as an oral combination approach to be tested in the first-line setting.

Other BCL-2 family inhibitors have also demonstrated activity in combination therapy in both hematologic malignancies and solid tumors. Venetoclax, a BCL-2 inhibitor, has been used in combination with ibrutinib, a BTK inhibitor, for hematologic malignancies, including mantle cell lymphoma and CLL (6, 22). In addition, a phase Ib trial of metastatic breast cancer demonstrated clinical activity of venetoclax combined with tamoxifen, supporting preclinical data suggesting that tamoxifen may sensitize breast cancer cells to apoptosis.

In conclusion, we found the combination of osimertinib plus navitoclax to be feasible in this first-in-human study with compelling clinical activity seen at the RP2D, supporting further studies of oral antiapoptotic agents and EGFR TKI combinations. There remains compelling need for combination approaches leveraging oral therapies that could further improve outcomes in oncogene-addicted NSCLC while maintaining the favorable quality of life afforded by these agents.

E.M. Bertino reports grants from NCI UM1 during the conduct of the study, as well as personal fees from Pfizer and nonfinancial support from Lilly, Merck, and Intellosphere outside the submitted work. R.D. Gentzler reports grants and nonfinancial support from NCI during the conduct of the study; grants from Pfizer, Merck, Bristol Myers Squibb, Takeda, Helsinn, and Jounce Therapeutics; personal fees and nonfinancial support from AstraZeneca, Pfizer, and Rockpointe CME; nonfinancial support from Syndax; personal fees from BluePrint Medicines, Targeted Oncology, and OncLive outside the submitted work. S. Clifford reports other from Foundation Medicine outside the submitted work. J. Kolesar reports grants from NCI during the conduct of the study, as well as grants from ArtemiFlow and nonfinancial support from ArtemiFlow and Helix Diagnostics outside the submitted work. E.B. Haura reports personal fees from Janssen and Amgen outside the submitted work. D.R. Camidge reports personal fees from Amgen, Anchiarno (SAB), Apollomics (SRC), AstraZeneca, Bio-Thera (DSMB), BMS, Daiichi-Sankyo (ILD adjudication committee), EMD Serono, Elevation (SRC), Eli Lilly, GSK, Helssin, Janssen, Onkure, Mersana, Pfizer, Qilu, Roche, Sanofi, Seattle Genetics, and Takeda outside the submitted work; and reports company sponsored trials at institution (PI roles), 2018–20: Abbvie, AstraZeneca, BMS, GSK, Hansoh, Inhibrx, Karyopharm, Lycera, Medimmune, Merck, Pfizer, Phosplatin, Psioxus, Rain, Roche/Genentech, Seattle Genetics, Symphogen, Takeda, and Tolero. T.E. Stinchcombe reports personal fees from AstraZeneca, Takeda, Genentech/Roche, Foundation Medicine, Pfizer, EMD Serono, Novartis, Daiichi Sankyo, Lilly, Medtronic, and Puma Biotechnology and grants from Genentech/Roche, Blueprint Medicines, AstraZeneca, Takeda, Advaxis, and Regeneron outside the submitted work. C. Hann reports grants and personal fees from AstraZeneca and AbbVie; grants from Amgen and GSK; personal fees from Ascentage; grants, personal fees, and other from Genentech/Roche and BMS outside the submitted work. J. Malhotra reports personal fees from AstraZeneca and Blueprint and grants from Biohaven Pharma, Bristol Meyers Squibb, Beyond Spring Pharmaceuticals, and Celldex outside the submitted work. L. Sholl reports personal fees from EMD Serono, Foghorn Therapeutics, and AstraZeneca and grants from Genentech outside the submitted work. G.I. Shapiro reports grants and personal fees from Eli Lilly, Merck KGaA/EMD-Serono, Sierra Oncology, and Pfizer; grants from Merck & Co.; personal fees from G1 Therapeutics, Roche, Bicycle Therapeutics, Fusion Pharmaceuticals, Cybrexa Therapeutics, Astex, Almac, Ipsen, Bayer, Angiex, Daiichi Sankyo, Seattle Genetics, Boehringer Ingelheim, ImmunoMet, Asana, Artios, Concarlo Holdings, Syros, Zentalis, and CytomX Therapeutics outside the submitted work; in addition, G.I. Shapiro has a patent for Dosage regimen for sapacitabine and seliciclib issued to Cyclacel Pharmaceuticals and has a patent for Compositions and methods for predicting response and resistance to CDK4/6 inhibition pending to Liam Cornell and Geoffrey Shapiro. P.A. Jänne reports grants and personal fees from AstraZeneca and personal fees from Abbvie during the conduct of the study; grants and personal fees from Boehringer Ingelheim, Eli Lilly, Daiichi Sankyo, and Takeda Oncology; personal fees from Pfizer, Roche/Genentech, Chugai Pharmaceuticals, Ignyta, Loxo Oncology, SFJ Pharmaceuticals, Voronoi, Biocartis, Novartis, Sanofi Oncology, Mirati Therapeutics, Transcenta, Silicon Therapeutics, and Syndax; grants from Revolution Medicines and Astellas Pharmaceuticals outside the submitted work; in addition, P.A. Jänne receives postmarketing royalties as an inventor on a DFCI owned patent on EGFR mutations issued and licensed to Lab Corp. G.R. Oxnard reports other from Foundation Medicine and Roche outside the submitted work. No disclosures were reported by the other authors.

E.M. Bertino: Resources, data curation, formal analysis, writing-original draft, project administration, writing-review and editing. R.D. Gentzler: Investigation, writing-original draft. S. Clifford: Resources, data curation. J. Kolesar: Formal analysis, investigation, writing-review and editing. A. Muzikansky: Resources, formal analysis, writing-review and editing. E.B. Haura: Investigation, writing-review and editing. Z. Piotrowska: Resources, data curation, writing-review and editing. D.R. Camidge: Resources, formal analysis, writing-review and editing. T.E. Stinchcombe: Investigation, writing-review and editing. C. Hann: Investigation, writing-review and editing. J. Malhotra: Investigation, writing-review and editing. L.C. Villaruz: Investigation, writing-review and editing. C.P. Paweletz: Resources, data curation, writing-review and editing. C.L. Lau: Investigation, writing-review and editing. L. Sholl: Investigation, writing-review and editing. N. Takebe: Conceptualization, project administration, writing-review and editing. J.A. Moscow: Resources, investigation, writing-review and editing. G.I. Shapiro: Investigation, writing-review and editing. P.A. Jänne: Conceptualization, data curation, formal analysis, supervision, funding acquisition, methodology, writing-original draft, project administration, writing-review and editing. G.R. Oxnard: Resources, formal analysis, supervision, funding acquisition, investigation, project administration, writing-review and editing.

This study was approved by the NCI-CTEP and funded by NCI grant UM1 CA186709 (to G.I. Shapiro), an NCI-CTEP UM1 CA 186709 Biomarker Supplement (to G.R. Oxnard and C.P. Paweletz), the Dana-Farber Cancer Institute-Brigham and Women's Hospital UM1 CA 186709 Biomarker/Molecular Characterization Hub (to L. Sholl), as well as NIH grant NIH R35 - R35CA220497 (to P.A. Jänne), and Damon Runyon Cancer Research Foundation grant CI-86–16 (to G.R. Oxnard). Additional funding in part from the Expect Miracles Foundation (to C.P. Paweletz) and the Robert and René Belfer Foundation (C.P. Paweletz).

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1.
Yu
HA
,
Arcila
ME
,
Rekhtman
N
,
Sima
CS
,
Zakowski
MF
,
Pao
W
, et al
Analysis of tumor specimens at the time of acquired resistance to EGFR-TKI therapy in 155 patients with EGFR-mutant lung cancers
.
Clin Cancer Res
2013
;
19
:
2240
7
.
2.
Korsmeyer
SJ
. 
BCL-2 gene family and the regulation of programmed cell death
.
Cancer Res
1999
;
59
:
1693s
1700s
.
3.
Korsmeyer
SJ
. 
Programmed cell death and the regulation of homeostasis
.
Harvey Lect
1999
;
95
:
21
41
.
4.
Korsmeyer
SJ
,
Gross
A
,
Harada
H
,
Zha
J
,
Wang
K
,
Yin
X-M
, et al
Death and survival signals determine active/inactive conformations of pro-apoptotic BAX, BAD, and BID molecules
.
Cold Spring Harb Symp Quant Biol
1999
;
64
:
343
50
.
5.
Cervantes-Gomez
F
,
Lamothe
B
,
Woyach
JA
,
Wierda
WG
,
Keating
MJ
,
Balakrishnan
K
, et al
Pharmacological and protein profiling suggests venetoclax (ABT-199) as optimal partner with ibrutinib in chronic lymphocytic leukemia
.
Clin Cancer Res
2015
;
21
:
3705
15
.
6.
Jain
N
,
Keating
M
,
Thompson
P
,
Ferrajoli
A
,
Burger
J
,
Borthakur
G
, et al
Ibrutinib and venetoclax for first-line treatment of CLL
.
N Engl J Med
2019
;
380
:
2095
103
.
7.
Kipps
TJ
,
Eradat
H
,
Grosicki
S
,
Catalano
J
,
Cosolo
W
,
Dyagil
IS
, et al
A phase 2 study of the BH3 mimetic BCL2 inhibitor navitoclax (ABT-263) with or without rituximab, in previously untreated B-cell chronic lymphocytic leukemia
.
Leuk Lymphoma
2015
;
56
:
2826
33
.
8.
Faber
AC
,
Corcoran
RB
,
Ebi
H
,
Sequist
LV
,
Waltman
BA
,
Chung
E
, et al
BIM expression in treatment-naive cancers predicts responsiveness to kinase inhibitors
.
Cancer Discov
2011
;
1
:
352
65
.
9.
Hata
AN
,
Niederst
MJ
,
Archibald
HL
,
Gomez-Caraballo
M
,
Siddiqui
FM
,
Mulvey
HE
, et al
Tumor cells can follow distinct evolutionary paths to become resistant to epidermal growth factor receptor inhibition
.
Nat Med
2016
;
22
:
262
9
.
10.
Eisenhauer
EA
,
Therasse
P
,
Bogaerts
J
,
Schwartz
LH
,
Sargent
D
,
Ford
R
, et al
New response evaluation criteria in solid tumours: revised RECIST guideline (version 1.1)
.
Eur J Cancer
2009
;
45
:
228
47
.
11.
Wilson
WH
,
O'Connor
OA
,
Czuczman
MS
,
LaCasce
AS
,
Gerecitano
JF
,
Leonard
JP
, et al
Navitoclax, a targeted high-affinity inhibitor of BCL-2, in lymphoid malignancies: a phase 1 dose-escalation study of safety, pharmacokinetics, pharmacodynamics, and antitumour activity
.
Lancet Oncol
2010
;
11
:
1149
59
.
12.
Gandhi
L
,
Camidge
DR
,
Ribeiro de Oliveira
M
,
Bonomi
P
,
Gandara
D
,
Khaira
D
, et al
Phase I study of Navitoclax (ABT-263), a novel Bcl-2 family inhibitor, in patients with small-cell lung cancer and other solid tumors
.
J Clin Oncol
2011
;
29
:
909
16
.
13.
Sholl
LM
,
Do
K
,
Shivdasani
P
,
Cerami
E
,
Dubuc
AM
,
Kuo
FC
, et al
Institutional implementation of clinical tumor profiling on an unselected cancer population
.
JCI Insight
2016
;
1
:
e87062
.
14.
Oxnard
GR
,
Paweletz
CP
,
Kuang
Y
,
Mach
SL
,
O'Connell
A
,
Messineo
MM
, et al
Noninvasive detection of response and resistance in EGFR-mutant lung cancer using quantitative next-generation genotyping of cell-free plasma DNA
.
Clin Cancer Res
2014
;
20
:
1698
1705
.
15.
MacLeod
AK
,
Lin
De
,
Huang
JT–J
,
McLaughlin
LA
,
Henderson
CJ
,
Wolf
CR
. 
Identification of novel pathways of osimertinib disposition and potential implications for the outcome of lung cancer therapy
.
Clin Cancer Res
2018
;
24
:
2138
47
.
16.
Yang
J
,
Pradhan
RS
,
Rosen
LS
,
Graham
AM
,
Holen
KD
,
Xiong
H
. 
Effect of rifampin on the pharmacokinetics, safety and tolerability of navitoclax (ABT-263), a dual inhibitor of Bcl-2 and Bcl-XL, in patients with cancer
.
J Clin Pharm Ther
2014
;
39
:
680
4
.
17.
Planchard
D
,
Brown
KH
,
Kim
D-W
,
Kim
S-We
,
Ohe
Y
,
Felip
E
, et al
Osimertinib Western and Asian clinical pharmacokinetics in patients and healthy volunteers: implications for formulation, dose, and dosing frequency in pivotal clinical studies
.
Cancer Chemother Pharmacol
2016
;
77
:
767
76
.
18.
Mok
TS
,
Wu
Yi-L
,
Ahn
M-Ju
,
Garassino
MC
,
Kim
HR
,
Ramalingam
SS
, et al
Osimertinib or platinum-pemetrexed in EGFR T790M-positive lung cancer
.
N Engl J Med
2017
;
376
:
629
40
.
19.
Ramalingam
SS
,
Yang
JC-H
,
Lee
CK
,
Kurata
T
,
Kim
D-W
,
John
T
, et al
Osimertinib as first-line treatment of EGFR mutation-positive advanced non-small-cell lung cancer
.
J Clin Oncol
2018
;
36
:
841
9
.
20.
Ramalingam
SS
,
Vansteenkiste
J
,
Planchard
D
,
Cho
BC
,
Gray
JE
,
Ohe
Y
, et al
Overall survival with osimertinib in untreated, EGFR-mutated advanced NSCLC
.
N Engl J Med
2020
;
382
:
41
50
.
21.
Soria
J-C
,
Ohe
Y
,
Vansteenkiste
J
,
Reungwetwattana
T
,
Chewaskulyong
B
,
Lee
KiH
, et al
Osimertinib in untreated EGFR-mutated advanced non-small-cell lung cancer
.
N Engl J Med
2018
;
378
:
113
25
.
22.
Tam
CS
,
Anderson
MA
,
Pott
C
,
Agarwal
R
,
Handunnetti
S
,
Hicks
RJ
, et al
Ibrutinib plus venetoclax for the treatment of mantle-cell lymphoma
.
N Engl J Med
2018
.
378
:
1211
23
.

Supplementary data