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Michael Offin
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P1.04 - Immuno-oncology (ID 164)
- Event: WCLC 2019
- Type: Poster Viewing in the Exhibit Hall
- Track: Immuno-oncology
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2019, 09:45 - 18:00, Exhibit Hall
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P1.04-39 - Molecular Characteristics, Immunophenotype, and Immune Checkpoint Inhibitor Response in BRAF Non-V600 Mutant Lung Cancers (ID 1529)
09:45 - 18:00 | Presenting Author(s): Michael Offin
- Abstract
Background
Targeted therapy for Class I BRAF mutant lung cancers (V600) is well described and there is growing literature on their response to immune checkpoint inhibitors (ICI). In contrast, the molecular characteristics, immunophenotype, and response rates of class II and III BRAF mutations are not well defined.
Method
Patients with BRAF Class I, II, III mutant and variants of unknown significance (VUS) lung cancers detected on NGS (MSK-IMPACT) from 1/2014-1/2018 were identified. PD-L1 by immunohistochemistry (E1L3N) was evaluated. Tumor mutation burden (TMB; mut/Mb) was determined by MSK-IMPACT. Best objective response to ICI was assessed by RECIST v1.1. Time to treatment discontinuation (TTD) and overall survival (OS) were assessed. Statistical analysis was performed with Fisher’s exact and Kaplan-Meier. BRAF V600 lung cancers were used as a comparator and analyzed separately from BRAF non-V600.
Result
6.0% (177/2962) of lung cancers harbored a BRAF-mutation. Median TMB of BRAF non-V600 mutant lung cancers was 10.8 mut/Mb (n=136) overall compared to 4.9 mut/Mb in V600 (n=41; p<0.0001) and 5.9 mut/Mb in BRAF wild-type patients (n=2785; p<0.0001). 69% (127/177) of BRAF-mutant cases were metastatic (29 Class I, 36 Class II, 23 Class III, and 39 VUS). 57% of patients were female, 82% were smokers, and 90% were adenocarcinoma. More smokers were seen in the BRAF V600 group than in the non-V600 group (n = 16 vs 88 respectively, p<0.0001). PD-L1 expression in 49 non-V600 cases with available tissue was 0%, 1-49%, and >50% in 59% (n=29), 31% (n=15), and 10% (n=5) respectively. 7 BRAF V600 cases with PDL1 testing had expression of 0%, 1-49%, and >50% in 2, 3, and 2 cases, respectively. No BRAF V600 cases had concurrent RAS/NF1-alterations compared to 11 non-V600 (p=0.07).
36 patients with BRAF non-V600 mutations received ICI (nivolumab (n=25), pembrolizumab (n=5), atezolizumab (n=2), ipilimumab/nivolumab (n=4); median line of therapy=2) with an ORR of 22% (8/36). 10 BRAF V600 mutant lung cancer patients received ICI (nivolumab (n=5), pembrolizumab (n=2), atezolizumab (n=1), ipilimumab/nivolumab (n=2); median line of therapy=2) with an ORR of 10% (1/10). There was no difference in ORR between non-V600 and V600 patients that received ICI (p=0.66). TTD in BRAF non-V600 was 3.2 months compared to 1.4 months for BRAF V600 mutant lung cancer patients (HR 0.59, p=0.26). Median TMB in patients with BRAF non-V600 mutations that responded vs those who did not was 13.2 and 10.8 mut/Mb respectively (p=0.92). One response to ICI was seen in a BRAF V600 with TMB of 19.3. OS of BRAF non-V600 patients was 1.7 years compared to 2.5 years in V600 (HR 1.25, p=0.38). OS was higher in BRAF non-V600 lung cancer patients who received ICI (2.4 years) compared to those that did not (1.2 years; HR 0.60, p=0.04).
Conclusion
The molecular characteristics and immunophenotype of BRAF non-V600 mutant lung cancers is typified by high TMB and low PD-L1 expression, with reasonably higher response rates and improved OS to later line ICI compared to BRAF V600. Further studies of immunotherapy in this oncogene subset is warranted.
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P1.14 - Targeted Therapy (ID 182)
- Event: WCLC 2019
- Type: Poster Viewing in the Exhibit Hall
- Track: Targeted Therapy
- Presentations: 2
- Moderators:
- Coordinates: 9/08/2019, 09:45 - 18:00, Exhibit Hall
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P1.14-06 - Tissue-Based Molecular and Histologic Landscape of Acquired Resistance to Osimertinib in Patients with EGFR-Mutant Lung Cancers (ID 1392)
09:45 - 18:00 | Author(s): Michael Offin
- Abstract
Background
Even though osimertinib (osi) is now the initial treatment for patients with EGFR-mutant lung cancers, our knowledge about mechanisms of resistance (MOR) is largely derived from patients who received osi after acquiring EGFR T790M on treatment with another EGFR inhibitor. Other studies of osi resistance have mainly reported genotyping of plasma which suboptimally detects lineage plasticity, copy number changes, and chromosomal rearrangements.
Method
To identify MOR to osi and characterize clinical, molecular and histologic factors associated with duration of response, we identified patients with EGFR-mutant lung cancers who had targeted next-generation sequencing (MSK-IMPACT) performed on tumor tissue obtained before treatment and after developing resistance to osi received as either first-line or later line EGFR-TKI.
Result
From January 2016 to March 2019, we collected paired pre-treatment and resistance specimens from 53 patients (1st line osi: 21. Osi after prior TKI: 32). MOR are summarized in the table. Histologic transformation was identified in 18% of 1st line cases and 17% of all cases. When osi was given as initial treatment, with median follow up of 18 months, early emerging MOR rarely included on-target resistance mechanisms (acquired EGFR G724S in 1/21). Other acquired alterations representing potential resistance mechanisms not listed in the table included CCNE1 and MYC amplifications, and mutations in MTOR A1098S and MET H1094Y.
ConclusionFirst line (n = 21)
Osi after prior TKI
(n = 32)
All
(n = 53)
Squamous transformation
3
3
6
Neuroendocrine transformation
1
2
3
On target mutation (EGFR C797X or other)
1
9
10
Loss of EGFR T790M only
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8
8
Fusions (ALK, RET, BRAF)
0
3
3
Amplifications (HER2, MET, EGFR)
2
3
4
Off target mutations (KRAS, BRAF, HER2)
1
2
3
In this analysis of MOR identified on NGS from tumor tissue, we found a spectrum of resistance mechanisms to osi. By evaluating tissue rather than plasma we provide data on histologic transformation (including squamous cell transformation). Subsequent studies are needed to assess patients with a longer time on initial osi as early progressors may have different MOR, with off-target MOR emerging earlier and on-target resistance mutations later.
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P1.14-12 - A Novel Activating MAP2K1 In-Frame Deletion Mediates Acquired Resistance to ROS1 TKIs in a Patient with ROS1 Fusion-Positive NSCLC (ID 2450)
09:45 - 18:00 | Author(s): Michael Offin
- Abstract
Background
ROS1 tyrosine kinase inhibitors (TKIs) such as crizotinib, entrectinib and lorlatinib provide significant benefit in non-small cell lung cancer (NSCLC) patients with ROS1 fusions. As observed with all targeted therapies however, resistance arises. With the widespread adoption of large panel next generation sequencing (NGS) at the time of acquired resistance (AR), our appreciation of novel off-target mechanisms continues to grow. Detecting additional mechanisms of acquired resistance (AR) is crucial to find novel therapies and improve patient outcomes.
Method
We reviewed targeted large-panel sequencing data (using the MSK-IMPACT assay) of paired pre-treatment and post-progression samples from patients treated with ROS1 TKIs. Genetic alterations hypothesized to confer AR were modeled in a patient-derived cell line (LUAD-0003, expressing EZR/ROS1) as well as isogenic human (HBEC) and murine (NIH-3T3) cell lines. ROS1 fusions were expressed in these cells either by cDNA overexpression (CD74/ROS1, SLC34A2/ROS1) or CRISPR-Cas9-mediated genomic engineering (EZR/ROS1). Using these cell line models, alterations in drug sensitivity and downstream signal pathways were examined. We also explored possible therapeutic strategies to overcome the drug resistance caused by the novel AR mechanisms examined in this study.
Result
We identified a patient with NSCLC harboring a MAP2K1 (MEK1) variant encoding an in-frame deletion of amino acids E41-L54 (MEK1del) in a sample taken at the time of resistance to lorlatinib (after 9 months’ treatment). This mutation was not detected in the pre-TKI sample. Induction of ROS1 fusions in HBEC and NIH-3T3 cells increased the sensitivity of these cells to ROS1 TKIs and stimulated activation of MEK/ERK signaling in comparison with AKT signaling, suggesting the importance of the RAS-MAPK pathway in driving ROS1 fusion-positive cancers. Underscoring the importance of the RAS-MAPK pathway in ROS1-mediated tumorigenesis, we identified three patients (pancreatic, salivary, and breast cancer) with a ROS1 fusion and NF1 loss-of-function mutation concurrently, in TKI-naïve samples. Expression of MEK1del in HBEC and NIH-3T3 cells harboring ROS1 fusions, and knockdown of NF1 in LUAD-0003, activated ERK signaling and conferred resistance to ROS1 TKIs. Combined targeting of ROS1 (crizotinib, lorlatinib) and MEK (selumetinib, trametinib) inhibited growth of cells expressing both ROS1 fusion and MEK1del.
Conclusion
Our results suggest that the activation of the RAS-MAPK pathway plays a critical role in tumorigenesis mediated by ROS1 fusions, and that activating mutations in this pathway can drive AR to ROS1 TKIs. Combined inhibition of ROS1 and MEK is a potential therapeutic strategy that should be explored clinically.
