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K. Thress
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MINI 10 - ALK and EGFR (ID 105)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:T. Yap, T. Li
- Coordinates: 9/07/2015, 16:45 - 18:15, Mile High Ballroom 1a-1f
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MINI10.12 - Preclinical Activity of AZD9291 in EGFR-Mutant NSCLC Brain Metastases (ID 410)
17:50 - 17:55 | Author(s): K. Thress
- Abstract
- Presentation
Background:
AZD9291 is an oral, potent, irreversible epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) selective for the EGFR-TKI-sensitizing (EGFRm) and T790M resistance mutations. We examined how the level of AZD9291 brain penetration and activity compared to that of other EGFR-TKIs in preclinical models of EGFRm non-small cell lung cancer (NSCLC) brain metastases (BM).
Methods:
Brain exposure of AZD9291 and an active circulating metabolite of AZD9291 (AZ5104), CO-1686 (rociletinib), gefitinib, erlotinib, and afatinib were evaluated in mouse models. Brain distribution following intravenous administration of microdoses (<3 micrograms) of [[11]C]AZD9291 and [[11]C]CO-1686 were compared in healthy cynomolgus macaques using positron emission tomography (PET) imaging. In vivo efficacy of AZD9291 and CO-1686 were assessed in a mouse EGFRm (exon 19 deletion) BM xenograft (PC9) model. Human doses that could potentially deliver BM efficacy were predicted using a preclinical pharmacokinetic/pharmacodynamic (PK/PD) mathematical model, adapted to account for the differential exposure and binding of AZD9291 and AZ5104 in brain compared with plasma.
Results:
In preclinical studies, AZD9291 showed significant exposure in the brain with concentrations in mouse brain tissue approximately 2-fold higher than plasma, although the metabolite, AZ5104, did not show similar levels of exposure to parent. AZD9291 also showed higher brain exposure than other tested EGFR-TKIs. Furthermore, under microdosing conditions [[11]C]AZD9291 showed marked exposure in a cynomolgus macaques brain PET study in contrast to [[11]C]CO-1686. At clinically relevant doses, AZD9291 distribution to the mouse brain was approximately 10-fold higher than gefitinib. In the PC9 BM model, AZD9291 showed tumor growth inhibition at 5 mg/kg/day. Using an adapted preclinical PK/PD model, simulations with clinical AZD9291/AZ5104 PK data predicted that a human dose of 80 mg may be sufficient to target EGFRm BM.
Conclusion:
Preclinical studies indicate AZD9291 has significant exposure in the brain and activity against EGFRm BM, compared with the other EGFR-TKIs tested. In light of early clinical activity of AZD9291 observed in patients with EGFRm NSCLC BM, further investigation into the potential benefit of AZD9291 in patients with EGFRm NSCLC BM is warranted.
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MINI 16 - EGFR Mutant Lung Cancer 2 (ID 130)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
- Moderators:G.J. Riely, M.C. Garassino
- Coordinates: 9/08/2015, 16:45 - 18:15, Four Seasons Ballroom F3+F4
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MINI16.09 - Design, Execution, and Preliminary Biomarker Results from Paired Tumor Biopsy Cohorts of the AZD9291 AURA Trial (ID 941)
17:30 - 17:35 | Author(s): K. Thress
- Abstract
Background:
Epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) exhibits sensitivity to EGFR tyrosine kinase inhibitors (TKIs) such as erlotinib and gefitinib; however, acquired resistance eventually develops in most patients. The most common mechanism of TKI resistance is a second-site mutation in the EGFR kinase domain, T790M. AZD9291 is an oral, potent, irreversible EGFR-TKI with potency against both T790M resistance and sensitizing EGFR mutations. In the ongoing Phase I AURA study (NCT01802632), AZD9291 induced durable responses in patients with acquired resistance to EGFR-TKIs. We report results of paired biopsy cohorts of the AURA trial, reviewing modulation of key molecular biomarkers of AZD9291 activity in patient tumor samples.
Methods:
Two cohorts of patients on the AURA trial were consented for collection of paired tumor biopsies. These patients had a pre-study tumor biopsy with T790M positive tumor status confirmed by central laboratory EGFR testing (Cobas™ EGFR Mutation Test). Following 8 to 15 days of once daily AZD9291 treatment (80 or 160 mg), a post-dose tumor biopsy was obtained. Baseline and post-dose tumor tissue was processed for routine histology and pathologic evaluation. More than 100 viable tumor cells per sample were required for subsequent biomarker scoring. Formalin-fixed paraffin-embedded tumor biopsies were profiled by immunohistochemistry with a suite of key pathway and tumor-relevant markers (phospho[p]-EGFR, pERK, pAKT, pS6, PD-L1, CD8). Matching plasma pharmacokinetic samples were also obtained for PK-PD correlations.
Results:
As of February 2015, 58 potential patients with an evaluable baseline biopsy were identified as candidates for post-dose biopsy collection. Sixteen of these patients did not proceed to an on-study biopsy as the identified lesions had regressed too substantially or were no longer considered suitable for re-biopsy, one patient was medically excluded from re-biopsy, and one patient’s sample was not available. In total, 40 patients supplied matched pre- and on-treatment biopsies. As of March 2015, paired tumor samples were available for QC from 26 of these 40 patients. Ten of these 26 biopsy specimens subsequently failed QC due to inadequate tumor content, leaving 16 paired tumor samples available for biomarker analyses, of which five have thus far been evaluated. AZD9291 treatment resulted in the inhibition of EGFR pathway components in the majority of post-treatment tumor biopsies. Tissue biomarker analyses are ongoing and updated data on evaluable biopsy pairs will be reported at the time of the congress.
Conclusion:
The completion of a paired biopsy cohort within the AURA trial was challenging due to the rapid onset of anti-tumor effects of AZD9291. Approximately 29% (17/58) of potentially eligible patients were unsuitable for the post-dose biopsy procedure due to tumor regression and 38% (10/26) of available post-dose biopsies were found to contain too little tumor for analysis. In the evaluable tumor pairs, pharmacodynamic modulation of the EGFR pathway was evident. Further biomarker analyses, including evidence of modulation of immune system markers, may help inform future combination strategies.
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ORAL 16 - Clinical Care of Lung Cancer and Advanced Biopsies (ID 115)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
- Moderators:J.W. Neal, Q. Zhou
- Coordinates: 9/08/2015, 10:45 - 12:15, Mile High Ballroom 2a-3b
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ORAL16.05 - Retrospective Analysis of ctDNA EGFR Mutations in the Phase III, Randomized IMPRESS Study (ID 2106)
11:28 - 11:39 | Author(s): K. Thress
- Abstract
- Presentation
Background:
The majority of patients with epidermal growth factor receptor (EGFR) mutation-positive non-small-cell lung cancer respond to first-line EGFR-tyrosine kinase inhibitors (EGFR-TKIs, e.g. gefitinib) but nearly all eventually acquire resistance. The most common mechanism of acquired resistance is a second-site mutation in the EGFR kinase domain, T790M. The phase III, double-blind IMPRESS study evaluated the efficacy and safety of continuing gefitinib plus pemetrexed/cisplatin versus placebo plus pemetrexed/cisplatin in patients with acquired resistance to first-line gefitinib. Study results did not support the continuation of gefitinib after disease progression (by RECIST criteria) when platinum-based doublet chemotherapy is used as second-line therapy. Here we report the results of a retrospective biomarker analysis of plasma circulating free, tumor-derived DNA (ctDNA) from patients in IMPRESS, including T790M profiling, to help understand the IMPRESS clinical trial outcome.
Methods:
Plasma samples for ctDNA isolation were collected at baseline and discontinuation from 151 randomized, non-Chinese patients in IMPRESS (58% of overall IMPRESS population). ctDNA levels of T790M, L858R, and Exon19 deletions were detected using both a quantitative emulsion (BEAMing) digital PCR assay (Sysmex[®]) and a qualitative QIAGEN[®] Therascreen ARMS assay (baseline only). Local EGFR tumor tissue (diagnostic) results were available for 133/151 patients. Mutation concordance rates between tissue and baseline plasma results, and comparisons between the two plasma detection methods, were calculated.
Results:
Baseline ctDNA EGFR mutation results were obtained for >99% (150/151) of patients. Using BEAMing, sensitivity and specificity between baseline plasma EGFR sensitizing mutations and local EGFR tumor tests were 78% (69/89) and 98% (42/43), respectively, for Exon19 deletions, and 82% (31/38) and 97% (91/94) for L858R. The T790M detection rate in baseline plasma samples using BEAMing was 56% (84/150). The Therascreen ARMS assay demonstrated a significantly reduced T790M detection rate of 13% (20/150). Likewise, the sensitivity of the Therascreen ARMS assay with respect to tissue for EGFR sensitizing mutations was also reduced compared with BEAMing: Exon 19: 54% (48/89), L858R: 47% (18/38), though the specificity remained near 100%. In the 97 evaluable plasma samples collected at discontinuation, T790M was detected by BEAMing in 52% (50/97) of patients. When compared with matched baseline plasma, 11 patients had newly acquired T790M mutation at discontinuation while T790M reverted to undetectable in 14 patients. Full plasma profiling data from the complete IMPRESS clinical study population (including 108 patients from China) and correlative analyses of plasma EGFR mutation status with clinical outcome (progression-free survival, overall survival, objective response rate) will be presented.
Conclusion:
In IMPRESS, T790M was detectable with BEAMing digital PCR in the baseline ctDNA samples of 56% of evaluable patients, a rate comparable to similar mutation analyses in this same second-line, EGFR-TKI-failed setting. EGFR mutation detection in plasma using the Therascreen ARMS assay demonstrated comparable specificity to BEAMing but reduced sensitivity. The T790M detection rate afforded by the BEAMing technology will allow for a comprehensive assessment of correlations between clinical outcome in IMPRESS and EGFR mutational status.
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ORAL 17 - EGFR Mutant Lung Cancer (ID 116)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 2
- Moderators:P. Meldgaard, E. Felip
- Coordinates: 9/08/2015, 10:45 - 12:15, Four Seasons Ballroom F3+F4
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ORAL17.07 - Mechanisms of Acquired Resistance to AZD9291 in EGFR T790M Positive Lung Cancer (ID 1365)
11:50 - 12:01 | Author(s): K. Thress
- Abstract
Background:
AZD9291 is an irreversible, mutant-selective epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) developed to have potency against both EGFR-sensitizing mutations and T790M. In the ongoing Phase I study of AZD9291 (AURA, NCT01802632), the response rate in patients with T790M positive lung cancer with disease progression on previous EGFR-TKI was >60%, with a preliminary median progression-free survival of >10 months. The molecular mechanisms underlying acquired resistance to AZD9291 are currently under investigation.
Methods:
Plasma genotyping was performed on patients from AURA who had progressed on AZD9291 if they had detectable T790M pre-AZD9291, as assessed by tumor or plasma genotyping, and if they had plasma collected at progression available for analysis. Cell-free DNA (cfDNA) was extracted from plasma taken at progression. Droplet digital PCR (ddPCR) was performed for EGFR exon 19 deletions, L858R, T790M, and C797S. For further exploration, next-generation sequencing (NGS) of an amplicon panel was performed on available progression cfDNA. Lastly, targeted NGS was performed on available resistance biopsy specimens.
Results:
Plasma specimens were available following disease progression on AZD9291 from 40 patients with tumors positive for T790M through tumor (33) or plasma genotyping (7). Twenty-six progression cfDNA specimens were positive for an EGFR-sensitizing mutation by ddPCR, and were deemed eligible for initial resistance analysis. Of these, 12 (46%) had no detectable T790M in plasma despite presence of the EGFR-sensitizing mutation, suggesting overgrowth of an alternate resistance mechanism. Seven patients had detectable C797S on ddPCR (27%), all with detectable T790M; of 14 with detectable T790M at resistance, C797S was only detected with EGFR exon 19 deletions (7/9) and not L858R (0/5, p=0.02). Plasma NGS was performed on 12 cases with acquired resistance that were T790M positive pretreatment. Exon 19 deletion/T790M/C797S were detected in four cases, with two of these harboring two different DNA mutations encoding for C797S. One case lost T790M and exhibited HER2 copy number gain (6.3 copies); a tumor biopsy from a separate case underwent aCGH at Institute Gustave Roussy and was also found to have focal HER2 amplification with loss of T790M. Targeted NGS was performed on resistance biopsies from a total of 10 patients from four centers with T790M positive biopsies pre-AZD9291. Six cases maintained T790M, with three harboring exon 19 del/T790M/C797S. In four cases with loss of T790M, one harbored BRAF V600E and one harbored PIK3CA E545K.
Conclusion:
Complementary genomic analysis of plasma and tumor DNA provides insight into the diverse molecular mechanisms of acquired resistance to AZD9291 in EGFR-mutant lung cancer. Our studies show that a majority of cases maintained T790M at resistance, at times acquiring a new C797S mutation in those with EGFR exon 19 deletion. Loss of T790M at progression may be mediated by overgrowth of cells harboring HER2 amplification, BRAF V600E, or PIK3CA mutations. These data highlight the need for investigation of combination therapies to effectively prevent or treat the complexity of drug resistance in EGFR-mutant lung cancer.
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ORAL17.08 - Gefitinib/Chemotherapy vs Chemotherapy in EGFR Mutation-Positive NSCLC Resistant to First-Line Gefitinib: IMPRESS T790M Subgroup Analysis (ID 3287)
12:01 - 12:12 | Author(s): K. Thress
- Abstract
- Presentation
Background:
Exon 20 T790M mutation is the most common cause of acquired resistance to first-line epidermal growth factor receptor tyrosine kinase inhibitors (EGFR TKIs). The IMPRESS study (NCT01544179; Phase III, double-blind IRESSA[TM ]Mutation Positive Multicentre Treatment Beyond ProgRESsion Study; Lancet Oncology: in press) reported no statistically significant difference in progression-free survival (PFS; primary endpoint) between gefitinib plus cisplatin/pemetrexed (cis/pem) (G) vs placebo plus cis/pem (P) in patients with acquired resistance to first-line gefitinib (hazard ratio [HR] 0.86; 95% confidence interval [CI] 0.65–1.13; p=0.273; median PFS 5.4 months in both arms) and other secondary endpoints. Among the subgroup analyses performed for IMPRESS, the most noticeable difference was observed by T790M status as tested via plasma circulating free tumor-derived DNA (ctDNA).
Methods:
Patients (age ≥18 years [Japan ≥20 years], chemotherapy-naïve, locally advanced/metastatic NSCLC with an activating EGFR mutation, prior disease progression on first-line gefitinib) from 71 centers (Europe/Asia Pacific) were randomized to G or P (gefitinib 250 mg/day or placebo, plus cis 75 mg/m[2]/pem 500 mg/m[2]). For biomarker analysis, consenting randomized patients provided 10-mL blood samples (at Visit 1 [baseline], 4, 6; then every 6 weeks and at discontinuation) from which to obtain ctDNA. ctDNA levels of EGFR mutations, including T790M, were detected using a quantitative emulsion (BEAMing) digital PCR assay (Sysmex[®]) conducted at a central laboratory (positivity defined as ≥0.02% mutant DNA fraction).
Results:
Data are reported for plasma samples from baseline visits (serial data will be available in the future). Blood samples were available for all 261 randomized patients, of whom T790M status was known for 247 (93.2%): T790M mutation-positive n=142 (57.5%; G=81, P=61) and T790M mutation negative n=105 (42.5%; G=46, P=59). Median PFS for the T790M mutation-positive subgroup was 4.6 vs 5.3 months for G and P, respectively (HR 0.97, 95% CI 0.67 to 1.42, p=0.8829). Median PFS for the T790M mutation-negative subgroup was 6.7 vs 5.4 months for G and P, respectively (HR 0.67, 95% CI 0.43 to 1.03, p=0.0745). See Table for additional study endpoints.
Conclusion:
Following acquired resistance to first-line gefitinib, these data suggest there were two distinct patient populations defined by T790M genotype. For plasma T790M-positive, gefitinib should not be continued when platinum-based doublet chemotherapy is used as second-line therapy. For plasma T790M-negative, continuation of gefitinib in combination with platinum-based doublet chemotherapy may offer clinical benefit, which would require further confirmation in a prospective randomized study.IMPRESS subgroup populations (plasma) T790M mutation-positive N=142 T790M mutation-negative N=105 ORR, % (G vs P) 28.4 vs 39.3 p=0.282 37.0 vs 27.1 p=0.171 DCR, % (G vs P) 81.5 vs 77.0 p=0.5175 93.5 vs 83.1 p=0.0895 OS, HR (95% CI)* 2.16 (1.26, 3.82) p=0.0067 0.83 (0.36, 1.85) p=0.6644 Plasma BEAMing PCR (compared with tumor), % (n/N) Exon 19 Deletions L858R Sensitivity 73.8 (124/168) 81.6 (62/76) Specificity 96.7 (89/92) 95.3 (161/169) Concordance 81.9 (213/260) 91.0 (224/247) *OS immature, follow up ongoing G: gefitinib plus cisplatin/pemetrexed; P: placebo plus cisplatin/pemetrexed ORR, objective response rate; DCR, disease control rate; OS, overall survival
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