Evaluation of the safety and tolerability of FTX-1821 for FSHD

Part A:
1. Healthy male / female subjects, 18 to 65 years of age, inclusive at screening;
2. Good health, based upon the results of medical history, physical examination, vital signs, ECG, and laboratory profiles of both blood and urine;
3. Body mass index (BMI) between 18 and 30 kg/m2, inclusive at screening, and with a minimum weight of 50 kg;
4. Willing to practice an approved method of birth control:
a. Females: Using 1 or more of the following acceptable methods of contraception: surgical sterilization (e.g., bilateral tubal ligation), intrauterine contraception/device, hormonal contraception, or any 2 barrier methods (a combination of male or female condom with diaphragm, sponge or cervical cap).
b. Males: Effective male contraception includes the use of condoms until 90 days after last dosing. Subjects with a vasectomy with negative semen analysis at follow up will use condoms until 7 days after last dosing.
5. Able and willing to provide written informed consent.
6. Willing and able to comply with all study procedures.
Part B:
1. Male / female subjects of 18 to 65 years of age, inclusive at screening, with a diagnosis of FSHD1 verified by (prior) genetic testing.
2. Clinical Severity Score between 1 and 4.5 on Ricci’s scale (scale range is from 0 to 5).
3. Good health, based upon the results of medical history, physical examination, vital signs, ECG, and laboratory profiles of both blood and urine;
4. Body mass index (BMI) between 18 and 35 kg/m2, inclusive at screening, and with a minimum weight of 50 kg;
5. Willing to practice an approved method of birth control:
a. Females: Using 1 or more of the following acceptable methods of contraception: surgical sterilization (e.g., bilateral tubal ligation), intrauterine contraception/device, hormonal contraception, or any 2 barrier methods (a combination of male or female condom with diaphragm, sponge or cervical cap).
b. Males: Effective male contraception includes the use of condoms until 90 days after last dosing. Subjects with a vasectomy with negative semen analysis at follow up will use condoms until 7 days after last dosing.
6. Able and willing to provide written informed consent.
7. Willing and able to comply with study procedures.
Part C:
Inclusion criteria for part C includes all of the criteria for Part B above, as well as the criteria below.
1. Has an MRI-eligible muscle for biopsy, as determined by the central reader.

Part A,B and C:
1. History of any illness or any clinical condition that, in the opinion of the investigator, might confound the results of the study or pose an additional risk in administering study drug to the subject. This may include, but is not limited to, history of relevant drug or food allergies; history of cardiovascular or central nervous system disease; history or presence of
clinically significant pathology; clinically significant history of mental disease; and history of cancer, except for squamous cell skin cancer, basal cell skin cancer, and Stage 0 cervical carcinoma in situ (all 3 with no recurrence for the last 5 years).
2. History of febrile illness within 5 days before the first study drug dose.
3. Current clinically significant liver or kidney dysfunction.
4. A screen positive for hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibody, or antibodies against human immunodeficiency viruses 1 and 2 (HIV 1/HIV 2 Abs).
5. Any condition possibly affecting drug absorption (e.g., gastrectomy, cholecystectomy, or other gastrointestinal tract surgery, except appendectomy).
6. Standard 12 lead ECG demonstrating QTcF >450 msec for male subjects and QTcF >470 msec for female subjects at screening. If QTcF exceeds 450 msec for males or 470 msec for females, the ECG will be repeated 2 more times, and the average of the 3 QTcF values will be used to determine the subject’s eligibility.
7. History of cardiac dysrhythmias requiring anti-arrhythmia treatment(s) or history or evidence of abnormal ECGs that, in the opinion of the investigator or medical monitor, would preclude the subject’s participation in the study.
8. Blood or blood product (e.g. plasma/serum) donation (of approximately 1 pint [500 mL] or more) or any significant loss of blood within three months (males) or four months (females) prior to screening or intention to donate blood or blood products during the study as determined by the investigator.
9. History of abuse of addictive substances such as drug abuse, or regular user of sedatives, hypnotics, tranquillizers, or any other addictive agent within 6 months prior to screening;
10. History of regular alcohol consumption within 6 months prior to screening defined as:
a. An average weekly intake of greater than 21 units. One unit is equivalent to a 285 mL glass of full-strength beer or 425 mL schooner of light beer or 1 (30 mL) measure of spirits or 1 glass (100 mL) of wine.
11. History of demonstrating an excess in xanthine consumption (more than eight cups of coffee or equivalent per day);
12. Participation in an interventional investigational drug or device study within 3 months prior to screening or more than 4 times in the past year;
13. For healthy volunteers (part A): Use of any medication (prescription or over-the-counter (OTC) within 14 days of study drug administration, or use of herbal supplements, dietary supplements or multivitamins within 7 days of study drug administration or less than five half-lives (whichever is longer), with the exception of contraceptives, hormonal replacement therapies, and paracetamol (up to 3g/day). Other exceptions will only be made if the rationale is clearly documented by the investigator;

For FSHD patients (part B and C): Medication that interferes with the study endpoints in the opinion of the investigator;
14. History of sensitivity to the study drug, or a history of drug or other allergy that, in the opinion of the investigator or Medical Monitor, contraindicated their participation.
15. Pregnant females as determined by positive urine human Chorionic Gonadotropin (hCG) test at screening or prior to first dose.
16. Lactating females.
17. Subject is mentally or legally incapacitated.
18. Abnormal laboratory results indicative of any significant medical disease that, in the opinion of the investigator, would preclude the subject's participation in the study at screening or prior to first dose.
19. Subject, or close relative of the subject, is the investigator or a subinvestigator, research assistant, pharmacist, study coordinator, or other staff directly involved with the conduct of the study at that site.
20. Positive test for drugs of abuse at screening or prior to first dose.
21. Subject smokes cigarettes (or equivalent) and/or has used nicotine-based products within 14 days prior to screening.
22. Consumption of any alcohol within the 48-hour period prior to study drug administration