This phase 1b study will determine the safety and efficacy of combined treatment of Abraxane and phenelzine sulfate (Nardil) for metastatic or locally advanced breast cancer.

Participants may be eligible to join this study if they are aged 18 years or above and have been diagnosed with metastatic breast cancer or inoperable locally advanced breast cancer.

All participants will receive a combination of intravenous Abraxane and an oral dose of phenelzine sulfate. Abraxane will be administered weekly for the first 3 weeks of a 4-week cycle for 3 consecutive cycles. Phenelzine sulfate will be taken daily for the duration of the 3 cycles. Five patient cohort groups will receive a progressively increasing dose of phenelzine sulfate. Safety and efficacy will be assessed weekly over the 3 cycles of treatment.

Although both drugs have been used in clinical care for more than a decade, they have not been intentionally combined together in a cancer therapy setting. This means that the combined effect of these two drugs has not been documented. This is being addressed in this study.

Nanoparticle albumin-bound paclitaxel (Abraxane) will be administered intravenously over 3 cycles at a fixed dosage of 100mg/m2 to each study participant. This dose will be administered weekly for the first 3 consecutive weeks, over the 4 week cycle, before commencing the second and third cycles.

In addition to the fixed dose of nanoparticle albumin-bound paclitaxel, all patients will receive a continuous daily oral dose of phenelzine sulfate across all three cycles,

Each of the five patient cohort groups will receive a progressively higher starting dose of phenelzine sulfate, consecutively. Cohort A will start at 15mg/day and will be increased to 30mg/d by week 2 and further increased to 45mg/d for week 3, which will be maintained throughout the study. Cohort B will start at 45mg/d and will be held constant throughout the Study. Similarly, Cohort C, D & E will start at 60, 75 and 90mg/d, respectively, and will also be held on this dose throughout the study. The decision to escalate the dose for the next cohort will be made on the basis of the number of dose limiting toxicity (DLT) events observed during the first 8 weeks in the preceding cohort group.

Phenelzine sulfate compliance will be monitored weekly based on drug tablet returns.

Inclusion Criteria:

1. Patients who are 18 years or older;
2. Fluent in written and spoken English and in a position to provide written informed consent to participate;
3. A patient who is in a position to attend a 12-week treatment regimen and end of study visit;
4. Metastatic Breast Cancer (MBC) or inoperable locally advanced breast cancer diagnosis based on pre-existing documented histopathology and medical imaging results, either Triple Negative Metastatic Breast Cancer (TNBC) or not;
5. Women with metastatic breast cancer or inoperable locally advanced breast cancer who have not received any cytotoxic therapy in the last 3 weeks;
6. Volunteers of child-bearing potential must have a negative serum pregnancy test (serum beta-human chorionic gonadotropin or ß-hCG) and have agreed to practice an effective, reliable contraceptive regimen for the duration of this clinical trial, such as an intrauterine device (IUD) or intrauterine system (IUS) with a failure rate of <1% stated on the product label or a male partner who is has been sterilised (vasectomy with documented azoospermia);
7. ECOG Performance Status 0 or 1; and
8. Adequate liver function as evidenced by bilirubin of <1.5 times upper limit of normal (ULN) and ALT/AST <2 times of ULN. However, AST and ALT of <5 times ULN if liver metastases are present.

Exclusion Criteria:

1. A patient who has been diagnosed as having HER2-positive metastatic breast cancer;
2. A concurrent condition that may limit the decision-making capabilities of the participant during the informed consent process;
3. A previous positive diagnosis of Human Immunodeficiency Virus (HIV) and/or Hepatitis C Virus (HCV) and/or Hepatitis B Virus (HBV) infection;
4. Women who are pregnant or lactating;
5. Uncontrolled, untreated intra-cranial metastases. However, controlled intra-cranial metastases are allowed, i.e. stable patients with more than a month after the completion of whole brain radiotherapy and not currently on steroids or anticonvulsants;
6. Current use of monoamine oxidase inhibitors (MOAI) or use of dextromethorphan
7. Current use of CNS depressants such as selective serotonin re-uptake inhibitors as well as specific medication for pain management including pethidine, tramadol, dextromethorphan, fentanyl and/or methadone. This includes the concurrent use of any serotoninergic agents or buspirone hydrochloride during the week preceding phenelzine sulfate administration, the active study treatment phase and the washout period at the end of study. Serotoninergic drugs may include but are not limited to the following: dexfenfluramine, fluoxetine, fluvoxamine, paroxetine, sertraline, citalopram and venlafaxine;
8. Previous use of nanoparticle albumin-bound paclitaxel;
9. Known allergy to phenelzine sulfate or similar MOAI; and
10. Known or suspected history of alcohol abuse;

It is the sponsors intention to publish the aggregated study results after the completion of the study.