Poziotinib hydrochloride is primarily used in the treatment of non-small cell lung cancer (NSCLC), particularly in cases where the cancer cells have specific genetic mutations, such as EGFR exon 20 insertions. It functions as a tyrosine kinase inhibitor, targeting and blocking the activity of mutated EGFR proteins that promote cancer cell growth. This helps in slowing down or stopping the progression of the disease. It is often considered when other treatments have not been effective or are unsuitable for the patient. Clinical studies continue to explore its efficacy and potential applications in other types of cancers with similar genetic alterations.