• Male or female ≥ 18 years of age and willing and able to provide informed consent

• Cytologically or histologically confirmed thymic carcinoma, which is incurable

• Received prior systemic therapy for thymic carcinoma, or is ineligible for or refuses other therapies

• Measurable disease, as per RECIST 1.1

• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1

• Absolute neutrophil count (ANC) ≥ 1.5 × 10\^9/L

• Platelets ≥ 100 × 10\^9/L

• Hemoglobin ≥ 9 g/dL or ≥ 5.6 mmol/L

• Serum creatinine ≤ 1.5 x upper limit of normal (ULN) OR measured or calculated creatinine clearance (CrCl) ≥ 50 mL/min (glomerular filtration rate \[GFR\] can also be used in place of creatinine or CrCl)

‣ Estimated glomerular filtration rate (eGFR) value ≥ 50 mL/min for participants with creatinine levels \> 1.5 x institutional ULN

⁃ Creatinine clearance may be calculated using the Cockcroft-Gault formula or estimated glomerular filtration rate (eGFR) may be calculated using the Modification of Diet in Renal Disease (MDRD) GFR equation

• Urine dipstick protein ˂ 2+ OR 24 hour urine protein quantification ˂ 1.0 g

• Serum total bilirubin ≤ 1.5 x ULN OR direct bilirubin ≤ ULN

• Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase \[SGOT\]) and alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase \[SGPT\]) ≤ 2.5 x ULN OR ≤ 5 x ULN for participants with liver metastases

• Albumin ≥ 2.5 g/dL

• International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 x ULN unless participant is receiving anticoagulant therapy, and then only as long as PT or partial thromboplastin time (PTT) is within therapeutic range of intended use of anticoagulants

• Activated partial thromboplastin time (aPTT) ≤ 1.5 x ULN unless participant is receiving anticoagulant therapy, and then only as long as PT or PTT is within therapeutic range of intended use of anticoagulants

• Female participants of childbearing potential must have a negative urine or serum pregnancy test. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required. The serum pregnancy test must be negative for the participant to be eligible. Female participants must agree to use a highly effective method of contraception from the beginning of screening until 120 days after the last dose of the ivonescimab, or be of non-childbearing potential. Non-childbearing potential is defined as follows (by other than medical reasons):

‣ ≥ 45 years of age and has not had menses for \> 2 years,

⁃ Participants who have been amenorrhoeic for \< 2 years without history of a hysterectomy and oophorectomy must have a follicle stimulating hormone value in the postmenopausal range upon screening evaluation, or

⁃ Post-hysterectomy, post-bilateral oophorectomy, or post-tubal ligation

• Unsterilized male patients having sex with a female partner of childbearing potential, or a pregnant or breastfeeding partner must agree to use barrier contraception (male condom) for the duration of the treatment period until 120 days after the last dose of ivonescimab. Male patients with female partners of childbearing potential must have the female partner agree to use at least 1 form of highly effective contraception for the duration of the treatment period until 120 days after the last dose of ivonescimab

• Male and female participants must agree not to donate sperm or eggs, respectively, from the first study-drug treatment through 120 days after the last study drug treatment

• Female participants must agree to not breastfeed during the study or for 120 days after the last dose of study treatment