The goal of this clinical trial is to evaluate the safety, tolerability and efficacy of human umbilical cord mesenchymal stem cell injection (HS_SW01 cells injection) in patients with Primary Ovarian Insufficiency (POI).

Participants will be required to sign the informed consent form and will only be assigned to the study and enrolled after undergoing a series of tests and meeting the inclusion and exclusion criteria of the protocol.

The goal of this clinical trial is to evaluate the safety, tolerability and efficacy of human umbilical cord mesenchymal stem cell injection (HS_SW01 cells injection) in patients with Primary Ovarian Insufficiency (POI).

Participants will be required to sign the informed consent form and will only be assigned to the study and enrolled after undergoing a series of tests and meeting the inclusion and exclusion criteria of the protocol.

This trial consists of a Phase I dose-escalation stage and a Phase II dose-expansion stage. Phase I is a randomized, double-blind, placebo-controlled design in which all participants receive background therapy plus a single intravenous infusion of HS_SW01 cells injection (1.0×10^6 cells/kg, 2.0×10^6 cells/kg, 3.0×10^6 cells/kg) or placebo, with 4-7 participants per dose group. A "3+3" dose-escalation design is used to evaluate safety, tolerability, pharmacokinetics, and immunogenicity across the three dose groups. In Phase II, the optimal biological dose (OBD) identified from the Phase I escalation study will serve as the recommended Phase II dose (RP2D) to preliminarily assess efficacy while continuing safety monitoring, providing a basis for subsequent clinical trials.

Eligible participants are patients with POI aged ≥18 to <40 years who meet all inclusion criteria and none of the exclusion criteria.

Inclusion Criteria:

1. Voluntarily sign the informed consent form;
2. Age ≥18 to <40 years, with oligomenorrhea or amenorrhea >4 months;
3. Serum baseline FSH >25 U/L (at least two measurements, interval >4 weeks);
4. Have received stable standard treatment for POI, such as ≥3 months of standardized hormone replacement therapy (HRT) with stable hormone levels;
5. No fertility requirement and adherence to strict contraception.

Exclusion Criteria:

1. Individuals with childbearing plans or those who are pregnant.

2. Genetic disorders, chromosomal abnormalities, or genetic defects known to cause premature ovarian insufficiency (POI).

3. Endocrine disorders affecting ovarian function, including polycystic ovary syndrome, hyperprolactinemia, hyperandrogenism, diabetes mellitus, and abnormalities of thyroid or adrenal function.

4. Presence of breast, uterine, or ovarian tumors; known or suspected sex hormone-dependent malignancies; or any other benign or malignant tumors.

5. Primary amenorrhea.

6. Uterine malformations.

7. Iatrogenic or drug-induced ovarian insufficiency.

8. Uncontrolled acute or chronic gynecological inflammation (including endometritis, etc.).

9. Bilateral endometrial thickness ≤8 mm after moderate-to-severe intrauterine adhesion surgery.

10. Complicated with endometriosis.

11. Severe functional impairment of major organs or coagulation disorders.

12. Active venous or arterial thromboembolic disease within the past 6 months.

13. Severe hepatic or renal insufficiency, etc.

14. Vaccination with live or live-attenuated vaccines within 2 months prior to enrollment.

15. Prior treatment with mesenchymal stem cells less than 3 months before enrollment.

16. Uncontrolled hypertension (>150/100 mmHg).

17. Any of the following conditions within 3 months prior to enrollment:

    1. Major trauma or major surgery (including joint surgery), or anticipated need for major surgery during the study period, which in the investigator's opinion poses unacceptable risk to the participant;
    2. Receipt of plasma exchange or extracorporeal photopheresis;
    3. Participation in any other interventional clinical trial.