Longitudinal Circulating Tumor DNA Analysis in Blood and Saliva for Prediction of Response to Osimertinib and Disease Progression in EGFR-Mutant Lung Adenocarcinoma.

Background: We assessed whether serial ctDNA monitoring of plasma and saliva predicts response and resistance to osimertinib in EGFR-mutant lung adenocarcinoma. Three ctDNA technologies-blood-based droplet-digital PCR (ddPCR), next-generation sequencing (NGS), and saliva-based EFIRM liquid biopsy (eLB)-were employed to investigate their complementary roles. Methods: Plasma and saliva samples were collected from patients enrolled in a prospective clinical trial of osimertinib and local ablative therapy upon progression (NCT02759835). Plasma was analyzed by ddPCR and NGS. Saliva was analyzed by eLB. Results: A total of 25 patients were included. We analyzed 534 samples by ddPCR (n = 25), 256 samples by NGS (n = 24) and 371 samples by eLB (n = 22). Among 20 patients who progressed, ctDNA progression predated RECIST 1.1 progression by a median of 118 days (range: 61-272 days) in 11 (55%) patients. Of nine patients without ctDNA progression by ddPCR, two patients had an increase in mutant EGFR by eLB and two patients were found to have ctDNA progression by NGS. Levels of ctDNA measured by ddPCR and NGS at early time points, but not volumetric tumor burden, were associated with PFS. EGFR/ERBB2/MET/KRAS amplifications, EGFR C797S, PIK3CA E545K, PTEN V9del, and CTNNB1 S45P were key resistance mechanisms identified by NGS. Conclusion: Serial assessment of ctDNA in plasma and saliva predicts response and resistance to osimertinib, with each assay having supplementary roles.

Clonal Evolution and Heterogeneity of Osimertinib Acquired Resistance Mechanisms in EGFR Mutant Lung Cancer.

Clonal evolution of osimertinib-resistance mechanisms in EGFR mutant lung adenocarcinoma is poorly understood. Using multi-region whole-exome and RNA sequencing of prospectively collected pre- and post-osimertinib-resistant tumors, including at rapid autopsies, we identify a likely mechanism driving osimertinib resistance in all patients analyzed. The majority of patients acquire two or more resistance mechanisms either concurrently or in temporal sequence. Focal copy-number amplifications occur subclonally and are spatially and temporally separated from common resistance mutations such as EGFR C797S. MET amplification occurs in 66% (n = 6/9) of first-line osimertinib-treated patients, albeit spatially heterogeneous, often co-occurs with additional acquired focal copy-number amplifications and is associated with early progression. Noteworthy osimertinib-resistance mechanisms discovered include neuroendocrine differentiation without histologic transformation, PD-L1, KRAS amplification, and ESR1-AKAP12, MKRN1-BRAF fusions. The subclonal co-occurrence of acquired genomic alterations upon osimertinib resistance will likely require targeting multiple resistance mechanisms by combination therapies.

Four-Week Direct-Acting Antiviral Regimens in Noncirrhotic Patients With Hepatitis C Virus Genotype 1 Infection: An Open-Label, Nonrandomized Trial.

BACKGROUND: Treatment of chronic hepatitis C virus (HCV) infection with direct-acting antivirals (DAAs) for 6 weeks achieves sustained virologic response (SVR) rates of 95% in some patients. If effective, shorter therapeutic courses could improve adherence and treatment costs. OBJECTIVE: To determine factors predictive of SVR to 4 weeks of DAA treatment in patients with stage F0 to F2 liver fibrosis. DESIGN: Open-label, nonrandomized, phase 2a trial. (Clinical Trials.gov: NCT01805882). SETTING: Single-center. PATIENTS: 50 treatment-naive and predominantly African American patients with HCV genotype 1 infection and early-stage liver fibrosis were sequentially enrolled into 2 treatment groups. INTERVENTION: 25 participants received a 3-drug regimen consisting of ledipasvir and sofosbuvir plus GS-9451 for 4 weeks, and 25 received a 4-drug regimen consisting of ledipasvir, sofosbuvir, GS-9451, and GS-9669 for 4 weeks. MEASUREMENTS: The primary efficacy end point was SVR12 (HCV RNA level below the lower limit of quantification at posttreatment week 12). RESULTS: Forty percent (10 of 25) (95% CI, 21% to 61%) of patients in the 3-drug group and 20% (5 of 25) (CI, 7% to 41%) of those in the 4-drug group achieved SVR12. Exploratory analysis suggested that lower baseline HCV viral load, younger age, and HCV genotype 1b were associated with SVR12. Ten patients had baseline HCV variants conferring greater than 20-fold resistance in vitro to at least 1 study DAA; all had viral relapse. Forty-eight percent (12 of 25) of patients receiving the 3-drug regimen and 72% (18 of 25) of those receiving the 4-drug regimen had adverse events, most of which were mild. One participant was lost to follow-up. LIMITATION: Nonrandomized study design and small sample of patients with early-stage fibrosis. CONCLUSION: Combination DAA therapy with 3 or 4 drugs for 4 weeks was well-tolerated but resulted in limited cure rates. PRIMARY FUNDING SOURCE: National Institute of Allergy and Infectious Diseases, National Cancer Institute, and Clinical Center Intramural Program; supported in part by a cooperative research and development agreement between the National Institutes of Health and Gilead Sciences.