Inclusion Criteria:
* Subjects ≥ 18 years at the first screening examination/visit.
* Subjects with advanced histologically or cytologically confirmed solid tumors (see below) refractory to or relapse from at least two previous therapies.
* Tumor types expected to express lower levels of FcRn relative to normal tissue including: STS, TNBC, cervical cancer, NSCLC, ovarian cancer, and KRAS mutated pancreatic ductal adenocarcinoma without requirement for testing FcRn level.
* Disease that is considered measurable by RECIST v1.1.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0-2.
* Life expectancy of at least 12 weeks.
* Human Immunodeficiency Virus (HIV)-positive trial participants should be on established antiretroviral therapy (ART) for at least four weeks and have an HIV viral load less than 400 copies/mL prior to enrollment.
* Left ventricular ejection fraction \> 50%.
* Adequate organ function: (Hb ≥10 g/dL, ANC ≥1,000/µL3, and platelets
≥100,000/µL3), serum bilirubin ≤.5x the institutional upper limit of normal (ULN) (unless known Gilbert's disease), Aspartate Aminotransferase (AST) and Alanine Aminotransferase (ALT) ≤3x ULN, and creatinine clearance \>50 mL/min as assessed by Cockcroft-Gault equation.
* For patients with known Gilbert's disease, serum unconjugated bilirubin must be \< 4 mg/dL.
* Patient must have washed out of prior chemotherapy (at least 3 weeks from last end of therapy), radiotherapy (at least 4 weeks from last end of therapy), immunotherapy (at least 4 weeks from last end of therapy), other targeted therapies (at least 4 weeks from last end of therapy), or surgery (at least 4 weeks).
* Recovery from toxicities of prior therapy. Toxicities should have recovered to CTCAE grade ≤ 1 or baseline with exception of alopecia.
* Females of reproductive potential must have had a negative pregnancy test performed within 7 days prior to the start of treatment. Additionally, female subjects of reproductive potential should agree to use effective acceptable forms of contraception: surgical sterilization (tubal ligation); total abstinence from sexual intercourse with the opposite sex; established hormonal birth control (e.g., oral, transdermal, injection, or implant) plus a barrier method or a double barrier method (intrauterine device, spermicide, or a diaphragm plus condom) for at least 1 month prior to Cycle 1 Day 1 and agreement to use such a method during study participation and for an additional 6 months after the last dose of SPEDOX-6.
* For males of reproductive potential: vasectomy or highly effective contraception (e.g., condoms, abstinence) during the study and for an additional 6 months after the last dose of SPEDOX-6.
Exclusion Criteria:
* Patients with cancers with known driver mutations for which there are known and effective targeted therapies that have not received those therapies, but are able to. If a patient has received appropriate targeted treatment for their mutations and progressed, or those treatments are contraindicated, they will be considered potentially eligible.
* Unstable angina pectoris, angioplasty, cardiac stenting, or myocardial infarction 6 months before study entry.
* Untreated metastases to the Central Nervous System (CNS).
* Have received any prior doxorubicin or anthracycline equivalent.
* Previous radiation to the mediastinal or pericardial area.
* A known allergy to albumin.
* HIV infection with CD4+ count \< 350 cells/µL or Acquired Immunodeficiency (AIDS)-defining opportunistic infection in previous 12 months.
* Pregnant (positive serum or urine pregnancy test) or lactating.
* Previous treatment with an investigational agent or the non-approved use of a drug or device withing 4 weeks of study entry.
* Uncontrolled diabetes mellitus.
* Patients who require concomitant use of strong inhibitors or inducers of CYP3A4, CYP2D6 or P-glycoprotein (P-gp).
