The purpose of the phase 1b portion is to evaluate safety and tolerability and determine a recommended phase 2 dose for TRC105 when added to standard dose sorafenib in patients with hepatocellular carcinoma. Up to 18 patients will be treated.

The purpose of the phase 2 portion is to estimate the ORR of patients with hepatocellular carcinoma by RECIST 1.1. Up to 21 patients will be treated in phase 2.

Sorafenib is an oral multikinase inhibitor targeting several receptor tyrosine kinases, including the VEGF receptor (VEGFR), implicated in pathologic angiogenesis, tumor growth, and cancer progression. Sorafenib is approved for the treatment of unresectable hepatocellular carcinoma (HCC). TRC105 is an antibody to endoglin, an important angiogenic target on proliferating endothelial cells that is distinct from VEGFR. TRC105 inhibits angiogenesis, tumor growth and metastases and complements the activity of bevacizumab and multi-kinase inhibitors that target the VEGFR in preclinical models. Together, the use of TRC105 with sorafenib may result in more effective angiogenesis inhibition and improved clinical efficacy over that seen with sorafenib alone.

Inclusion Criteria:

1. Patients must have confirmed hepatocellular carcinoma (HCC) by histopathology or imaging criteria according to AASLD guidelines.
2. Patients must have disease that is not amenable to potentially curative resection or ablative techniques or that has recurred following ablative techniques. In addition, disease must not be amenable to transhepatic arterial chemoembolization (TACE) or must have progressed on TACE. Patients must not be candidates for liver transplantation.
3. If liver cirrhosis is present, patient must have a Child-Pugh A or B (7 points) classification.
4. No other prior malignancy is allowed except for the following: adequately treated basal cell or squamous cell skin cancer, adequately treated Stage I or II cancer from which the patient is currently in complete remission per investigators' clinical judgment.
5. Measurable disease by RECIST 1.1 (Phase 2 only)
6. Age of 18 years or older
7. ECOG performance status ≤ 1
8. Resolution of all acute adverse events resulting from prior cancer therapies to NCI CTCAE grade ≤ 1 or baseline
9. Adequate organ function
10. Willingness and ability to consent to participate in study
11. Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures
12. Men who are sterile OR agree to use at least two forms of a reliable and highly effective method of birth control and to not donate sperm and for at least 180 days following last dose of TRC105 or sorafenib.
13. Woman of non-child bearing potential due to surgical sterilization confirmed by medical history or menopause, OR woman of child bearing potential who test negative for pregnancy at time of enrollment based on serum pregnancy test and agree to use at least 2 forms of a reliable and highly effective method of birth control during the study and for at least 180 days after stopping TRC105 or sorafenib.

Exclusion Criteria:

1. Prior anticancer systemic therapy
2. Current treatment on another therapeutic clinical trial
3. Prior radiation therapy within 28 days of starting the study treatment
4. No major surgical procedure or significant traumatic injury within 6 weeks prior to study registration, and must have fully recovered from any such procedure.
5. Proteinuria
6. Uncontrolled chronic hypertension defined as systolic > 150 or diastolic > 90 despite optimal therapy.
7. History of brain involvement with cancer, spinal cord compression, or carcinomatous meningitis, or new evidence of brain or leptomeningeal disease.
8. Angina, MI, symptomatic congestive heart failure, cerebrovascular accident, transient ischemic attack, arterial embolism, pulmonary embolism, PTCA or CABG within the past 6 months.
9. Active bleeding or pathologic condition that carries a high risk of bleeding. No bleeding diathesis.
10. Thrombolytic use within 10 days prior to first day of study therapy
11. History of hemorrhage or hemoptysis (> ½ teaspoon bright red blood) within 3 months of starting study treatment
12. Need for anticoagulation
13. History of liver transplant
14. History of bleeding esophageal varices in previous 6 months, which have not been adequately managed with banding or sclerotherapy.
15. History of peptic ulcer disease within 3 months of treatment.
16. Known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) related illness
17. Patients may not have received a strong CYP3A4 inducer within 12 days prior to registration
18. Patients with known hypersensitivity to Chinese hamster ovary products or other recombinant human, chimeric, or humanized antibodies.
19. Other severe acute or chronic medical or psychiatric condition or laboratory abnormality
20. Ascites or pleural effusion requiring intervention or that required intervention within the last month and has recurred
21. Pericardial effusion (except trace effusion identified by echocardiogram)

Patients who received at least a portion of a dose of Carotuximab

Adverse events were collected while on study and for 28 days following the last dose of TRC105 or sorafenib. The longest duration of participation of any patient on study was 24 months.

Only patients who received at least a portion of a dose of TRC105 or sorafenib were included in the safety population. Both dose groups received 10 mg/kg TRC105 for the first month. Patients assigned to the 10 mg/kg weekly (cycle 1) then 15 mg/kg every two weeks (cycle 2+) dose group who discontinued the study prior to initiating cycle 2 dosing were counted in the 10 mg/kg weekly adverse event group.

TRC105 development has been discontinued due to lack of efficacy. Secondary endpoints including PFS, OS, duration of response, sorafenib PK, circulating angiogenic biomarkers and assessment of IGF-1-modified Child-Pugh score were not performed.