Histologically confirmed recurrent/metastatic TNBC (ER-negative: IHC ER \<1%; PR-negative: IHC PR \<1%; HER2-negative: IHC -/+, or IHC ++ but FISH/CISH negative), with at least one measurable lesion per RECIST v1.1.
ECOG performance status 0-2.
Estimated life expectancy ≥3 months.
Received first-line chemotherapy + PD-1/PD-L1 inhibitor for metastatic or locally advanced unresectable TNBC, with response of CR/PR or stable disease lasting ≥3 months. For neoadjuvant/adjuvant therapy, disease progression during treatment or within 6 months after completion will be considered as first-line failure.
Adequate organ function (no transfusion, growth factor, or thrombopoietic agents within 2 weeks before screening):
Serum chemistry: TBIL ≤1.5×ULN; ALT and AST ≤1.5×ULN; ALP ≤2.5×ULN; BUN and Cr ≤1.5×ULN with creatinine clearance ≥50 mL/min (Cockcroft-Gault).
TSH ≤ULN (if abnormal, T3 and T4 must be assessed; enrollment allowed if T3/T4 normal).
Cardiac: LVEF ≥50% by echocardiography; 18-lead ECG with QTcF \<480 ms (female).
Women of childbearing potential must have negative pregnancy test (serum or urine) within 7 days prior to enrollment and agree to use adequate contraception during treatment and for 4 months after last dose.
Voluntarily signed informed consent and good compliance.
You may not be if
Concurrent participation in another interventional cancer trial.
Received other antitumor therapy within 14 days before first dose.
Prior treatment with pirfenidone.
Untreated active brain metastases or leptomeningeal disease.
Major non-breast cancer surgery within 4 weeks prior to enrollment or incomplete recovery from such surgery.
Active or history of autoimmune disease (except vitiligo, resolved childhood asthma without treatment in adulthood).
