A Study to Assess the Safety, Tolerability, and Pharmacokinetics of Ascending, Subcutaneous, Single and Multiple Doses of SHP681 (Glucagon-like Peptide-2 [GLP-2] Analog-Fc Fusion) in Healthy Adult Participants

The purpose of the study is to assess the safety and tolerability of single and multiple ascending subcutaneous (SC) doses of SHP681 in healthy adult participants.

The study consists of a single ascending dose (SAD) portion and a multiple ascending dose (MAD) portion.

The study duration for the SAD portion of the study consists of a screening period of up to 28 days and 1 treatment period of 29 days. SAD portion of the study contains 5 cohorts and dose escalation will proceed sequentially to assess the following single SC doses of SHP681 or SHP681 matched placebo: 0.2 milligram per kilogram (mg/kg), 0.5 mg/kg, 1 mg/kg, 2 mg/kg, and 4 mg/kg.

The study duration of the MAD portion comprises of a screening period up to 28 days and a treatment period of 57 days for each cohort. MAD portion of the study contains 6 cohorts and dose escalation will proceed sequentially to assess the following SC doses of SHP681 or SHP681 matched placebo: 0.2 mg/kg, 0.5 mg/kg, 1 mg/kg, 2 mg/kg, and 4 mg/kg once weekly for 5 weeks till 5 cohorts and the 6th cohort will receive 4 mg/kg SHP681 or matched placebo every 2 weeks over a 6-week period (3 doses).

Eligibility Criteria:
Inclusion Criteria:

* Ability to voluntarily provide written, signed, and dated informed consent to participate in the study.
* An understanding, ability, and willingness to fully comply with study procedures and restrictions.
* Age 18-50 inclusive at the time of consent. The date of signature of the informed consent is defined as the beginning of the screening period. This inclusion criterion will only be assessed at the first screening visit.
* Male, or non-pregnant, non-lactating female who agrees to comply with any applicable contraceptive requirements of the protocol or females of non-childbearing potential.
* Considered "healthy" by the investigator. Healthy status is defined by absence of evidence of any active or chronic disease or condition based on a detailed medical and surgical history, a complete physical examination including vital signs, 12-lead electrocardiogram (ECG), hematology, blood chemistry, and urinalysis.
* Body mass index between 18.0 kilograms per square meter (kg/m\^2) and 30.0 kg/m\^2 inclusive with a body weight 50-100 kg (110-220 pounds \[lbs\]). This inclusion criterion will only be assessed at the first screening visit.

Exclusion Criteria:

* History of any hematological, hepatic, respiratory, cardiovascular, renal, neurological or psychiatric disease, gall bladder removal, or current or recurrent disease that could affect the action, absorption, or disposition of the investigational product, or clinical or laboratory assessments.
* Current or relevant history of physical or psychiatric illness, any medical disorder that may require treatment or render the participant unlikely to fully complete the study, or any condition that presents undue risk from the investigational product or procedures.
* Known or suspected intolerance or hypersensitivity to the investigational product(s), closely-related compounds, or any of the stated ingredients.
* Significant illness, as judged by the investigator, within 2 weeks of the first dose of investigational product.
* Known history of alcohol or other substance abuse within the last year.
* Donation of blood or blood products (example \[eg\], plasma or platelets) within 60 days prior to receiving the first dose of investigational product.
* Within 30 days prior to the first dose of investigational product:

  1. Have used an investigational product (if elimination half-life is less than (\<) 6 days, otherwise 5 half-lives).
  2. Have been enrolled in a clinical study.
  3. Have had any substantial changes in eating habits, as assessed by the investigator.
* Use of dipeptidyl peptidase (DPP)-4 inhibitors within 30 days or 5 half-lives, whichever is greater, prior to administration of the investigational product.
* Confirmed systolic blood pressure greater than (\>) 139 millimeters of mercury (mmHg) or \<89mmHg, and diastolic blood pressure \> 89mmHg or \<49 mmHg.
* Twelve-lead ECG demonstrating corrected QT interval by Fredericia (QTcF) \>450 millisecond (msec) at screening. If QTcF exceeds 450 msec, the ECG should be repeated 2 more times and the average of the 3 QTcF values should be used to determine the participant's eligibility.
* Positive screen for alcohol or illicit drugs at screening or Day -1.
* Male participants who consume more than 21 units of alcohol per week or 3 units per day. Female participants who consume more than 14 units of alcohol per week or 2 units per day.

  (1 alcohol unit equal to \[=\] 1 beer or 1 wine (5 ounce \[oz\] per 150 milliliter \[mL\]) or 1 liquor (1.5 oz/40 mL) or 0.75 oz alcohol).
* Positive human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), or hepatitis C virus (HCV) antibody screen.
* Use of tobacco in any form (eg, smoking or chewing) or other nicotine-containing products in any form (eg, gum, patch). Ex-users must report that they have stopped using tobacco for at least 30 days prior to receiving the first dose of investigational product.
* Routine consumption of more than 2 units of caffeine per day or participants who experience headaches associated with caffeine withdrawal. (1 caffeine unit is contained in the following items: one 6 oz (180 mL) cup of coffee, two 12 oz (360 mL) cans of cola, one 12 oz cup of tea, three 1 oz (85 g) chocolate bars. Decaffeinated coffee, tea, or cola are not considered to contain caffeine).
* Prior screen failure (unless Sponsor approval is given), randomization, participation, or enrollment in this study or prior exposure to any GLP-2 analogs.
* Unresected gastrointestinal (GI) polyp, known polyposis condition, or premalignant changes in the GI tract.
* Any history of malignancy in the GI tract or treatment for any other malignancy in the previous 5 years.
* Current use of any medication (including over-the-counter, herbal, or homeopathic preparations; with the exception of hormonal replacement therapy or hormonal contraceptives and occasional use of ibuprofen or acetaminophen and pre-approved medication for sedation or other medications required during or after the endoscopy). Current use is defined as use within 14 days of the first dose of investigational product.
* Findings of subclinical hepatobiliary disease, such as gallstones, on abdominal ultrasound at screening as determined by the Investigator in consultation with the Medical Monitor.