STP705 injections to reduce submental fat

Inclusion Criteria:

* Aged 18 to 65 years of age, inclusive, at the time of Screening.
* Body mass index of ≤ 40.0 kg/m2.
* Good general health, in the opinion of the Investigator or designee, with no clinically significant medical history, and have no clinically significant abnormalities on physical examination, electrocardiogram (ECGs), or laboratory assessments at Screening and/or before the first administration of the IP.
* Grade 2 or 3 Submental fat, as assessed by the Investigator using the Clinician-Reported-Submental Fat Rating Scale (CR-SMFRS) AND as assessed by the participant using the Participant-Reported- Submental Fat Rating Scale (PR-SMFRS).
* Dissatisfaction with the submental area, as assessed by the participant as a rating of 0, 1, or 2 using the Participant-Self Satisfaction Scale (PSSS).
* History of stable body weight for at least 6 months (+/- 5 kg) prior to first dosing with the IP.
* Woman of childbearing potential (WOCBP) or fertile man agrees to use an acceptable method of contraception from the start of Screening until 90 days after the last dose of IP. Acceptable methods of contraception are defined in .
* Agrees to refrain from making significant changes, in the judgement of the Investigator, to dietary or exercise habits during the study.
* Agrees to forego any treatment or behaviour (eg, unshaven facial hair) during the participation inthe study that may affect the assessments of the submental area.
* No clinically significant abnormalities at Screening on clinical and laboratory tests, at the discretion of the Investigator.
* Able and willing to attend the necessary visits to the study site.
* Able and willing to provide written informed consent after the nature of the study has been explained and prior to the commencement of any study procedures.

Exclusion Criteria:

* History of any intervention to treat Submental fat (eg, liposuction, surgery, or lipolytic agents).
* Treatment with botulinum toxin injections in the neck or chin area within 6 months prior to the first dosing with the IP through the end of study (EOS).
* History of trauma associated with the chin or neck areas that in the judgement of the Investigator may affect evaluation of safety or efficacy of treatment.
* Evidence of any cause of enlargement in the submental area (eg, thyroid enlargement, cervical adenopathy) other than localised Submental fat.
* A Submental Skin Laxity Grade (SMSLG) of 4 or other anatomical feature (eg, predominant subplatysmal fat, loose skin in the neck or chin area, prominent platysmal bands), as assessed within 28 days prior to the first dosing with the IP, for which reduction in Submental fat may, in the judgement of the Investigator, result in an aesthetically unacceptable outcome.
* Treatment with radio frequency, laser procedures, ultrasound, chemical peels, or dermal fillers in the neck or chin area within 12 months prior to first dosing with the IP and through the end of study(EOS).
* History or current symptoms of dysphagia. 8. Any medical condition (eg, respiratory, cardiovascular, hepatic, neurological disease, or thyroid dysfunction) that (in the opinion of the Investigator) would interfere with assessment of safety or efficacy or compromise the participant's ability to undergo study procedures or give informed consent.
* History of severe allergic or anaphylactic reactions, or sensitivity to the IP or its constituents.
* Treatment with an investigational device or agent within 30 days prior to the first dosing with the IP and through the end of study(EOS).
* Blood or plasma donation or had significant blood loss (\> 500 mL) within 30 days prior to the first dosing with the IP.
* History of severe Type I-IV hypersensitivity reactions.
* History of cytokine release syndrome (CRS).
* History of marginal mandibular nerve injury.
* History or current lower facial weakness and/or lower facial asymmetry.
* Pregnancy, breastfeeding, or planning to breastfeed during the study and for at least 90 days (approximately 5 half-lives of the study drug) after the last dose of study treatment.
* Unwillingness to use medically acceptable methods of contraception during the study and for at least 90 days after the last dose of study treatment.
* Presence of genetic or endocrine disorders associated with obesity that are not amenable to submental fat reduction, including but not limited to Cohen syndrome, Alström syndrome, Prader-Willi syndrome, untreated hypothyroidism, Cushing's syndrome, or lipodystrophy syndromes.
* Active dermatitis, open wounds, or infection in the treatment area.
* Medical conditions affecting platelet function or coagulation.
* Use of medications that affect coagulation or platelet function within 14 days prior to the first dosing of the IP, or unwillingness to abstain from such medications through the end of study(EOS).
* Use of tanning beds and/or excessive sun exposure within 14 days prior to the first dosing of the IP, or unwillingness to abstain from these during the study through the end of study(EOS).