This is a Phase 2a, randomized, double-blind, placebo-controlled, 14-day repeat oral, dose ranging study to determine the safety, pharmacokinetics (PK) and pharmacodynamics (PD) effects of SP-304 in patients with chronic idiopathic constipation.

This is a Phase 2a, randomized, double-blind, placebo-controlled, 14-day repeat oral, dose ranging study to determine the safety, PK and PD effects of SP-304 in patients with chronic idiopathic constipation. Patients diagnosed with chronic idiopathic constipation (CIC) will be screened for the anticipated 4 cohorts, to yield 80 randomized patients for enrollment. Four dose cohorts are planned (0.3 mg, 1.0 mg, 3.0mg, and 9.0 mg) with 20 patients per dose cohort [randomization ratio 3:1 (15 receive SP-304:5 receive placebo)]. Patients who continue to meet all the entry criteria and complete the pre-treatment bowel movement (BM) diary will receive, in a double-blind, randomized fashion, SP-304 or matching placebo. It is expected that each patient will complete all 14 days of dosing (including making accurate BM diary entries for all 14 days in the treatment period). All patients receiving at least one dose of SP-304 or matching placebo will be considered evaluable for the safety endpoints. If a patient receives at least 5 doses per treatment week (1 dose per day for 7 days) and has completed BM diary entries for those 5 dosing days in each corresponding treatment week, he/she will be considered evaluable.

Inclusion Criteria:

• Subject is able to understand and willing to sign the Informed Consent Form (ICF) and capable of providing written authorization for use and disclosure of protected health information per requirements of 45 CFR 164.508 (Health Insurance Portability and Accountability Act [HIPAA]).
• Subject is male or non-pregnant, non-breastfeeding female, between 18 and 75 years of age (inclusive) at the time of first dose.
• Subject has a body mass index (BMI) between 18 and 35 kg/m2.
• Subject meets the Rome III Diagnostic Criteria for constipation (Drossman, 2006) for the past 3 months with symptom onset > 6 months prior to diagnosis.

Exclusion Criteria:

• Subject reports loose stool (fluffy pieces with ragged edges, a mushy stool) or watery stool (no solid pieces, entirely liquid; BSFS score of 6 or 7, respectively) in the absence of any laxative, enema, suppository or prohibited medicine for > 25% of BMs during the 3 months prior to the Screening visit and during the 14 day pre-treatment period.
• Subjects who meet the Rome III criteria for IBS.
• Subject has failed to complete the pre-treatment bowel movement diary accurately and completely during the pre-treatment period prior to Day 1 dosing.

Any publication of the results, either in part or in total (e.g., articles in journals or newspapers, oral presentations, abstracts) by the Investigator(s) or their representative(s), shall require prior notification, review, within a reasonable time frame, and written approval by the Sponsor. Additionally such publications cannot be made in violation of the Sponsor's confidentiality restrictions or to the detriment of the Sponsor's intellectual property rights.