This study is designed to formally evaluate the impact of famotidine, an H2R antagonist, on the pharmacokinetics of telaglenastat.

This study will be conducted in up to 22 healthy volunteers, who meet all of the inclusion criteria and none of the exclusion criteria. The study is double-blinded, randomized 2-way crossover in design.

Subjects will receive four 200 mg tablets of telaglenastat either in the presence or absence of 20 mg famotidine (H2R-antagonist) with a 4-day wash-out period in between each regimen.

Inclusion Criteria:

1. Healthy adult male or female, 18-55 years of age, inclusive, at screening.

2. Has not used nicotine-containing products (more than 5 cigarettes/equivalent per week) for at least 3 months prior the first dose and has negative urine cotinine tests at screening, Day 1 and Day 7.

3. Body mass index (BMI) between 18.0 and 32.0 kg/m2, inclusively, at screening.

4. Medically healthy with no clinically significant medical history, physical examination, laboratory profiles, vital signs, or ECGs, as deemed by the Principal Investigator (PI).

5. For a female of childbearing potential: either be sexually inactive (abstinent - ie, not sexually active with a male partner) for 14 days prior to the first dose and through 14 days following the last dose of any study drug(s) or be using one of the following acceptable birth control methods:

   1. Non-hormone releasing intrauterine device in place for at least 3 months prior to the first dose of any study drug with a physical barrier method (eg, condom, diaphragm) from the time of screening through the last dose of any study drug. A progesterone (progestin)-only contraceptive is allowable.
   2. A physical barrier method (eg, condom, diaphragm) for at least 14 days prior to the first dose of any study drug and until the last dose of any study drug.

6. In addition, female subjects of childbearing potential will be advised to remain sexually inactive or to keep the same birth control method until the last dose of any study drug.

7. Females of non-childbearing potential as defined below do not require contraception.

   Females of non-childbearing potential:

   1. must have undergone one of the following sterilization procedures at least 6 months prior to the first dose of any study drug:

      1. hysteroscopic sterilization;
      2. bilateral salpingectomy;
   1. Women with a tubal ligation less than one year prior to study start must agree to use a barrier method of birth control 3. non-surgical transcervical sterilization (eg, Essure®); 4. hysterectomy; 5. bilateral oophorectomy OR
   2. be postmenopausal with amenorrhea for at least 1 year prior to the first telaglenastat dose with follicle-stimulating hormone (FSH) serum levels > 30 IU/mL.

8. A non-vasectomized male subject must agree to use a physical barrier (eg, condom or diaphragm) or abstain from sexual intercourse with female partners during the study until the last dose of any study drug. (No restrictions are required for a vasectomized male provided his vasectomy has been performed 4 months or more prior to study start. A male who has been vasectomized less than 4 months prior to study start must follow the same restrictions as a non-vasectomized male).

   a) Female participants with a vasectomized male partner, or male participants with a female partner of non-childbearing potential do not require contraception.

9. If male, must agree not to donate sperm from dosing until the last dose of any study drug.

10. Alanine and aspartate aminotransferase and bilirubin levels ≤ the upper limit of normal or deemed not clinically significant by the Investigator.

11. Understands the study procedures in the informed consent form (ICF) and be willing and able to comply with the protocol.

Exclusion Criteria:

1. Subject is mentally or legally incapacitated or has significant emotional problems at the time of the screening visit or is expected to manifest significant emotional problems during the conduct of the study.

2. History or presence of clinically significant medical or psychiatric condition or disease in the opinion of the PI.

3. History of any illness that, in the opinion of the PI, might confound the results of the study or poses an additional risk to the subject by their participation in the study.

4. History or presence of alcoholism or drug abuse within the past 2 years prior to screening.

5. History or presence of hypersensitivity or idiosyncratic reaction to the study drugs or inactive ingredient(s).

6. History or presence of:

   1. liver disease, pancreatic insufficiency or intestinal malabsorption;
   2. neuropathy or muscle disorders;
   3. seizures;
   4. asthma; childhood asthma that has resolved and has not required medical treatment for at least 5 years prior to study start is permitted;
   5. fluid retention;
   6. cardiovascular disease, cardiac arrhythmias, hypertension, cardiovascular thrombotic events, myocardial infarction, or stroke;
   7. ulcer disease or gastrointestinal bleeding;
   8. renal papillary necrosis and other renal injury;
   9. exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis.

7. Female subjects who are pregnant or lactating.

8. Positive urine drug or alcohol results at screening or check-in.

9. Positive urine cotinine at screening or check-in.

10. Positive results at screening for HIV types 1 and 2, HBsAg, or hepatitus C virus.

11. Seated blood pressure (taken after 5 minutes in a sitting position) is less than 90/40 mmHg or greater than 140/90 mmHg at screening and not as part of ECG.

12. Seated heart rate (taken after 5 minutes in a sitting position) is lower than 40 bpm or higher than 100 bpm at screening and not as part of ECG.

13. QTcF interval is > 460 msec (males) or > 480 msec (females) or deemed clinically abnormal by the PI at screening.

14. Estimated creatinine clearance < 90 mL/min calculated by the method of Cockcroft and Gault at screening.

15. Unable to refrain from or anticipates the use of:

    1. Proton pump inhibitors (PPIs), histamine H2 receptor antagonists (H2RAs), buffering agents (eg, Tums) or any other medication that may have an effect on gastric acid secretion beginning 14 days prior to the first dose of any study drug and throughout the study.
    2. Any non-prescription medications, herbal remedies, or vitamin supplements beginning 14 days prior to the first dose of any study drug and throughout the study.
    3. Any prescription medications (including hormone replacement therapy and lithium) beginning 14 days prior to the first dose of any study drug and throughout the study.

16. Donation of blood or significant blood loss within 56 days prior to the first dose of any study drug.

17. Plasma donation within 14 days prior to the first dose of any study drug.

18. Presence of any medical history or condition that may limit gastric drug absorption (eg, prior gastric surgery, gastric banding, Whipple procedure)

19. Participation in another clinical trial within 28 days prior to the first dose of any study drug. The 28-day window will be derived from the date of the last blood collection or dosing, whichever is later, in the previous study to Day 1 of Period 1 of the current study.

Famotidine or Placebo for famotidine