52 Week Study + 24-Month Long-Term Extension of Safety, PK, & Efficacy of XYOSTED® for Testosterone Replacement in Male Adolescents With Hypogonadism

Inclusion Criteria:

1. Diagnosed with a deficiency or absence of endogenous testosterone due to primary orsecondary hypogonadism of a known etiology. Children with combined hormonedeficiencies are permitted to enroll (but the child must already be receivingtreatment for concomitant hormonal deficiencies)

2. Participants receiving prior testosterone treatment must be receiving a stable dosefor at least 12 weeks prior to Screening. Treatment naive participants are permittedto enroll.

3. Have parent(s) or a legal guardian who will voluntarily provide written informedconsent for the child to participate in the study

4. Willing to provide assent for participation in the study

5. Be a male 12 to < 18 years of age at the time of consent/assent

6. Have Legally Authorized Representative who is able to understand and comply with allstudy procedures and agrees to have the child participate in the study program asoutlined in the protocol

7. Requires chronic pharmacologic support for the initiation and/or continuation ofpubertal maturation

8. Have a body mass index (BMI)-for-age greater than the 5th percentile and weigh ≥ 30kg.

9. If sexually active with a female partner of child-bearing potential, agrees to:

10. Practice true abstinence including 30 days after the last IP administration,or,

11. Use 2 adequate forms of highly effective contraception, one of which should bea physical barrier, during the study and for 30 days after the last IPadministration.

Exclusion Criteria:

1. Has abnormal thyroid function tests at Screening. May supplement per usual clinicalpractice and rescreen up to two times.

2. Has suspected or known constitutional growth delay in growth and puberty (CDGP)

3. Has evidence of possible nutritional or gastrointestinal disorder that may impactgrowth (e.g., abrupt weight loss within the 3 months prior to Screening, unmanagedceliac disease, inflammatory bowel disease)

4. Has a known allergy or hypersensitivity to XYOSTED, or to any of its ingredients (testosterone enanthate and sesame oil)

5. Participants receiving prior treatment with testosterone who are not on a stabledose for at least 12 weeks prior to Screening.

6. Has an allergy to foods or products containing sesame seeds or sesame oil

7. Has Stage 1 hypertension, defined as the average of 2 or more seated right arm BPmeasurements exceeding the 95th percentile for age, sex, and height, or SBP ≥ 130 mmHg and/or DBP ≥ 80 mm Hg at Screening or Day 1.

8. Has a clinically significant abnormal clinical laboratory test value at Screening,as determined by the Investigator including hematocrit > 48%, or >50% for patientsliving at high altitude if not receiving testosterone treatment, or hematocrit > 52%if already receiving testosterone treatment.

9. Has a history of deep venous thrombosis or pulmonary embolism

10. Has evidence of a clinically significant 12-lead electrocardiogram (ECG) abnormalityat Screening, as determined by the Investigator

11. Has a current suspected or diagnosed (and unresected) tumor of the pituitary glandwith the exception of Rathke's cleft cyst or a stable non-functioning pituitarymicroadenoma (ie, lesion size < 10 mm that has not increased in size over a periodof 1 year on repeat imaging), as determined by the Investigator

12. Has an active malignancy or has received treatment for a malignancy within the 12months before Screening

13. Is currently receiving antipsychotic medication for any reason or is currentlyreceiving selective serotonin reuptake inhibitor (SSRI) medication for depression

14. Is receiving any other medication or has a condition that would preclude safeparticipation in the study or confound the evaluation of safety, as determined bythe Investigator

15. Has a history of suicidal behavior (i.e., actions intended to harm oneself),suicidal ideation (i.e., thoughts and plans about suicide), or suicide attempts

16. Has any affirmative responses on the Columbia Suicide Severity Rating Scale (C-SSRS)questionnaire to questions #3, #4, or #5 or any affirmative response to questions #1or #2 within the past 12 months on the suicide ideation questions (first section) ORany affirmative response on the suicidal behavior questions (the second section).

17. Is currently taking supraphysiologic doses of systemic glucocorticoids for more than 3 weeks, except for intermittent short courses of exogenous glucocorticoids asneeded for the treatment of asthma

18. Has received any other investigational compound within 1 month prior to screening or 5 half-lives of the investigational product (whichever is longer)

19. Has received gonadotropin-releasing hormone (GnRH) agonists, aromatase inhibitors,androgens (eg, dehydroepiandrosterone [DHEA]), anabolic steroids such asoxandrolone, or other sex steroids within 12 months before the Screening visit, orwould require these treatments at any time during the study.

20. Receiving cytochrome P450 (CYP) 3A4 or P glycoprotein (P-gp) inhibitors/inducers ormedications that are metabolized by CYP3A4 or P-gp within 30 days of enrolment.

21. Has a history of alcohol or drug abuse

22. Has a history or clinical manifestations of significant renal, hepatic,cardiovascular, metabolic, neurologic, psychiatric, or other conditions that wouldpreclude participation in the study, as determined by the Investigator

23. Has chronic urticaria or dermatographism

24. Has 25-hydroxy-vitamin D blood level < 20 ng/mL. Participants with initial vitamin Dblood measurement < 20 ng/mL may enroll while they receive supplementation perclinical practice