Leronlimab (PRO 140) Combined With Carboplatin in Patients With Cytokine Chemokine Receptor 5 Positive (CCR5+) mTNBC

Inclusion Criteria:

1. Must have a histologically confirmed diagnosis of TNBC. Must demonstrate HER-2 negative (IHC 0, 1+, or fluorescence in situ hybridization (FISH) negative and ER\<1%, and PR \< 1%, per ASCO/CAP criteria);
2. Demonstrate CCR5 + by IHC (\>10% membranous staining completed at the reference laboratory of Dr. Hallgeir Rui at Medical College of Wisconsin).

   Note: This test will be done as part of the pre-screening period. It will be performed in archival metastatic tissue. If archival tissue is not available then, fresh biopsy will be done;
3. Be willing to provide tissue from a newly obtained core or excisional biopsy of a tumor lesion (in case archival tissue is not available);
4. Patients with stage IV de-novo disease or patients that develop recurrence after completion of neoadjuvant or adjuvant therapy are eligible; Note: Patients who have been exposed to carboplatin in neoadjuvant or adjuvant setting will be allowed to enroll, if they have progressed ≥ 6 months from completion of treatment.
5. Phase 1 study section:

   Subjects must have disease recurrence and progression after ≤ 2 line of therapy in metastatic setting but untreated with carboplatin;

   Phase 2 study section:

   Subjects must be naive to chemotherapy or untreated with carboplatin in metastatic setting (first-line) OR excluding carboplatin chemotherapy, subjects must have failed first-line combination of chemotherapy and a checkpoint inhibitor in metastatic setting;
6. Patients must have measurable disease based on RECIST v1.1;
7. Female patients, ≥ 18 years of age;
8. Patients must exhibit a/an ECOG performance status of 0-1;
9. Life expectancy of at least 6 months;
10. Patients must have adequate organ and bone marrow function within 28 days prior to registration, as defined below:

    * leukocytes ≥ 3,000/mcL;
    * absolute neutrophil count ≥ 1,500/mcL;
    * platelets ≥ 100,000/mcL;
    * total bilirubin: within normal institutional limits;
    * AST(SGOT) \&ALT(SPGT) ≤ 2.5 X institutional upper limit of normal (ULN) (applicable to all patients, irrespective of liver disease or metastasis); and
    * creatinine: within normal institutional limits.
11. Clinically normal resting 12-lead ECG at Screening Visit or, if abnormal, considered not clinically significant by the Principal Investigator.
12. Females of child-bearing potential (FOCBP) and males must agree to use two medically accepted methods of contraception with hormonal or barrier method of birth control, or abstinence, prior to study entry, for the duration of study participation and for 60 days after the last dose of study drug (Refer to Appendix 1). Should a female patient become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. Note: A FOCBP is any woman (regardless of sexual orientation, having undergone a tubal ligation, or remaining celibate by choice) who meets the following criteria:

    * Has not undergone a hysterectomy or bilateral oophorectomy; and
    * Has had menses at any time in the preceding 12 consecutive months (and therefore has not been naturally postmenopausal for \> 12 months).
13. FOCBP must have a negative serum pregnancy test at Screening Visit and negative urine pregnancy test prior to receiving the first dose of study drug; and
14. Patients must have the ability to understand and the willingness to sign a written informed consent prior to registration on study.

Exclusion Criteria:

1. HER-2 overexpressed/amplified metastatic breast cancer (MBC) (Appendix 2 for guidelines from ASCO);
2. ER and or PR expressing tumors;
3. Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 28 days prior to enrollment;
4. Patients who have a history of allergic reactions attributed to compounds of similar chemical or biologic composition to leronlimab (PRO 140) are not eligible;
5. Patients who have had prior exposure to CCR5 antagonists are not eligible;
6. Patients who have a known additional malignancy that is progressing or requires active treatment are not eligible. Patients who have had a prior diagnosis of cancer and if it has been \<3 years since their last treatment are not eligible. Exceptions include basal cell carcinoma of the skin or squamous cell carcinoma of the skin that has undergone potentially curative therapy or in situ cervical cancer;
7. Has an active infection requiring systemic therapy. Note: Patients must complete any treatment with antibiotics prior to registration;
8. Patients who have a known HIV positive status or known/ active Hepatitis B and/or C infection are not eligible;
9. Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis. Note: Subjects with previously treated brain metastases may participate provided they are stable (without evidence of progression by imaging for at least four weeks prior to the first dose of trial treatment and any neurologic symptoms have returned to baseline), have no evidence of new or enlarging brain metastases, and are not using steroids for at least 7 days prior to trial treatment. This exception does not include carcinomatous meningitis which is excluded regardless of clinical stability;
10. Has a history or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the trial, interfere with the subject's participation for the full duration of the trial, or is not in the best interest of the subject to participate, in the opinion of the treating investigator;
11. Has known psychiatric or substance abuse disorders that would interfere with cooperation with the requirements of the trial; and
12. Is pregnant or breastfeeding, or expecting to conceive or have children within the projected duration of the trial, starting with the pre-screening or screening visit through the duration of study participation.