Achalasia Type II on High-Resolution Manometry

A 45-year-old man from rural India presents with a 2-year history of progressive dysphagia to both solids and liquids, nocturnal regurgitation of undigested food, and a 6 kg weight loss. Upper endoscopy shows a dilated esophagus with retained food and a puckered lower esophageal sphincter (LES), with biopsies excluding malignancy. High-resolution manometry (HRM) is performed and the pattern marked **B** in the diagram is identified: 100% failed peristalsis with ≥20% of swallows demonstrating uniform pressurization spanning from the upper esophageal sphincter to the LES at ≥30 mmHg. Based on this HRM finding, which of the following therapeutic approaches is most likely to yield the BEST long-term response in this patient?