The EndoStim Stimulation System is an investigational device intended to improve the lower esophageal sphincter (LES) resting tone and restore LES function in individuals suffering with gastroesophageal reflux disease (GERD).

EndoStim is developing an investigational medical device specifically designed to deliver electrical stimulation to the LES and has completed two clinical feasibility studies using the EndoStim stimulation system in fifteen subjects.

Acute electrical stimulation resulted in significant LES pressure with no adverse effects reported.

Results of these studies are promising and warrant additional clinical study to evaluate the effectiveness of EndoStim stimulation system to treat GERD over time.

In this study, EndoStim proposes using a fully implantable system. Results of this study are expected to provide confirmation of safety of long-term LES stimulation and may provide long term clinical benefit for GERD patients.

Inclusion Criteria:

• Subject is between 21 - 65 years of age.
• Subject has a history of heartburn, regurgitation or both for > 6 months prompting physician recommendation of continual daily use of PPI before study entry.
• Baseline GERD-HRQL heartburn score of ≥ 20 off PPI assessed during the run-in phase.
• Subject has an American Society of Anesthesiologists (ASA) Physical Status Classification I or II (or comparable local classification if any).
• Subject has demonstrated satisfactory symptomatic response to a previous course of GERD therapy (≥ 2 weeks); GERD HRQL heartburn score improvement of ≥ 10 on therapy as assessed during the run in phase.
• Subject has exhibited excessive lower esophageal acid exposure during 24-hour pH-metry off antisecretory therapy performed within 6 months of enrollment; pH < 4 for > 5% of total or > 3% of supine time.
• Subject has a resting LES end expiratory pressure > 5mm Hg and < 15 mm Hg on a high resolution manometry within 6 months of enrollment.
• Subject has esophagitis ≤ Grade C (LA classification) on upper endoscopy within 6 months of enrollment.
• Subject has esophageal body contraction amplitude > 30 mmHg for > 70% of swallows and > 50% peristaltic contractions on high resolution manometry.
• Subject has signed the informed consent form.

Exclusion Criteria:

• Subject has non-GERD esophageal motility disorders.
• Subject has gastroparesis.
• Subject has significant multisystem diseases.
• Subject has scleroderma requiring therapy in the preceding 2 years .
• Subject has dermatomyositis requiring therapy in the preceding 2 years.
• Subject has Calcinosis-Raynaud's-esophaguschlerodactyly syndrome requiring therapy in the preceding 2 years.
• Subject has Sjogren's Syndrome requiring therapy in the preceding 2 years.
• Subject has Sharp's Syndrome requiring therapy in the preceding 2 years.
• Subject has persistent esophagitis greater than LA grade C.
• Subject has Barrett's epithelium (> M2; >C1) or any dysplasia.
• Subject has a hiatus hernia larger than 3 cm.
• Subject has a body mass Index greater than 35 kg/m2 .
• Subject has Type 1 diabetes mellitus
• Subject has uncontrolled Type 2 diabetes mellitus (T2DM) defined as HbA1c >9.5 in the previous 6 months, or has T2DM for > 10 years.
• Subject has an autoimmune disorder requiring therapy in the preceding 2 years.
• Subject has suspected or confirmed esophageal or gastric cancer.
• Subject has esophageal or gastric varices.
• Subject has significant cardiac arrhythmia or ectopy or significant cardiovascular disease.
• Subject has an existing implanted electrical stimulator (e.g., pacemaker).
• Subject requires chronic anticoagulant therapy.
• Subject has dysphagia or esophageal peptic structure, excluding Schatzki's ring.
• Subject is pregnant or intends to become pregnant during the trial period.
• Subject is currently enrolled in other potentially confounding research.
• Subject has any condition that, at the discretion of the investigator, would preclude participation in the trial.
• History of any malignancy in the last 2 years
• History of previous esophageal or gastric surgery, including nissen fundoplication