PQ203 in Advanced Malignant Tumors Including Triple Negative Breast Cancer

Inclusion Criteria: * At least 18 years old * Histologically or cytologically documented metastatic or locally advanced solid tumor malignancies having progressed through or being otherwise ineligible to receive approved standard-of-care therapies * Eastern Cooperative Oncology Group (ECOG) performance status of 0-1 * Documented presence of RECIST v1.1 measurable disease * Adequate organ function confirmed by the following laboratory values obtained within 14 days of the first dose of PQ203: Bone Marrow Function * Absolute neutrophil count (ANC) ≥ 1.5 × 10e9/L * Platelets \> 100 × 10e9/L * Hemoglobin ≥ 9 g/dL Hepatic Function * AST, alanine transaminase ALT or ALP ≤ 2.5 × upper limit of normal (ULN); if liver metastases, then ≤ 5 × ULN * Bilirubin ≤ 1.5 × ULN (\< 2 × ULN if hyperbilirubinemia is due to Gilbert's syndrome) * Serum albumin ≥ 35 g/L (3.5 g/dL) Renal Function * Calculated creatinine clearance of ≥ 60 mL/min by the Cockcroft-Gault equation * Urine protein \< 2+ Cardiac Function • Left ventricular ejection fraction (LVEF) ≥ 50% Other * Understand and voluntarily sign an Institutional Review Board (IRB)/Independent Ethics Committee (IEC)/Research Ethics Board (REB)-approved informed consent form prior to any study-specific evaluation. * PT/PTT or INR \<1.2x upper limit of normal * Non-surgically sterile men and women of child bearing potential must agree to use highly effective methods of contraception for at least 4 months beyond the final dose received. * Toxicity of previous antitumor therapy has returned to Grade ≤1 Exclusion Criteria: * Patients with primary central nervous system (CNS) malignancies (Patients with stable brain metastases (≥ 4 weeks after a treatment) not requiring steroids or other treatment will be allowed on study). * Blood transfusion within 14 days of study treatment * Serious comorbid medical conditions such as heart, lung, kidney, liver, and brain disease that, in the opinion of the enrolling investigator, could interfere with study treatment * Subjects with history of severe heart disease * QTc interval using Fridericia's formula (QTcF) \> 470 ms * Estimated or known weight \> 115 kg (253 lbs) * Known/suspected pregnancy and/or lactation * Diastolic blood pressure \< 60 mmHg or \>110 mmHg * Uncontrolled intercurrent illness * Long term care facility resident or prisoner * Any prior receipt of a MMAE-containing drug * Any prior receipt of a SORT1-targeting medication * Participation in another clinical study investigating a drug or medical device or a neuro-interventional or surgical procedure that is not considered as standard care in the 30 days preceding study enrolment * Treatment with any of the following: * Chemotherapy or other systemic anti-cancer therapy ≤14 days or 5 half-lives (whichever is shorter) prior to first dose of study drug except for Nitrosoureas or mitomycins ≤42 days * Major surgery ≤28 days from first dose of study drug * Patients with a history of cerebrovascular accident within 6 months of planned first dose. * Patients with clinically symptomatic ocular toxicities * Patients with history of (noninfectious) interstitial lung disease (ILD)/pneumonitis that require steroids, with current ILD/pneumonitis, or where suspected ILD/pneumonitis cannot be ruled out by imaging at screening * Patients with active Grade \>1 peripheral neuropathy