• \- Age ≥ 18 years; ER/PgR expression ≤10% and low HER2 expression (IHC 1+, or IHC 2+ and ISH-); Advanced breast cancer patients; Prior treatment with ≥1 line of therapy for localized recurrence or metastatic disease; At least one prior treatment with taxane or anthracycline therapy; Allowed to receive immunotherapy during neoadjuvant or adjuvant stages; Measurable lesions according to RECIST 1.1 standards; ECOG PS score: 0-1; Voluntary participation with good compliance; Negative pregnancy test result, childbearing-age participants commit to effective contraception from the study start to 6 months after the last dose; Adequate organ function; Blood routine: ANC ≥1.5×109/L, PLT≥70×109/L, HGB ≥90g/L; Liver function: TBIL ≤1.5×ULN, ALT and AST ≤3×ULN, serum albumin ≥28 g/L, ALP ≤5×ULN; Stable liver function for at least 1 week after routine liver protection treatment, as assessed by the investigator, is eligible for inclusion; Renal function: Cr ≤1.5×ULN, or CrCl ≥50 mL/min (using standard Cockcroft-Gault formula); Coagulation function: INR ≤1.5/PT ≤1.5×ULN, aPTT ≤1.5×ULN; Left ventricular ejection fraction ≥50%