Acquired resistance to prior EGFR TKIs is considered as "unmet medical need" in clinical practice. To evaluate the efficacy of NOV120101 (Poziotinib) as a second-line monotherapeutic agent, patients with acquired resistance to gefitinib or erlotinib will be enrolled in this study. Subjects will receive NOV120101 (Poziotinib) 16 mg PO once daily until disease progression or unacceptable toxicity development. Progression free survival (PFS) will be analyzed as the primary endpoint in this trial. Secondary endpoints including PFS rate at 16 weeks, ORR and DCR will also be analyzed.