Monotherapy Inclusion Criteria (Parts A and B)

- Histologically- or cytologically-confirmed advanced or metastatic malignancy, defined
as:

- One of the following tumor types:

- Unresectable locally-advanced or metastatic non-small cell lung cancer
(NSCLC), gastric/gastroesophageal (GE) junction carcinoma, cutaneous
melanoma, head and neck squamous cell carcinoma (HNSCC), bladder cancer,
cervical cancer, ovarian cancer, or triple negative breast cancer (TNBC)

- Lymphomas, including:

- Classical Hodgkin lymphoma (cHL)

- Diffuse large B-cell lymphoma (DLBCL)

- Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS)

- Lymphoma: Participants should have disease progression on or after treatment
with standard therapies expected to provide benefit in the judgement of the
investigator.

- cHL: Participants must have received at least 3 prior systemic
therapies. Participants should have had disease recurrence or
progression following brentuximab vedotin therapy or have been
ineligible to receive brentuximab vedotin. Participants who have not
received autologous stem cell transplant (SCT) must have refused or
been deemed ineligible. Participants should have received or not be
eligible to have received an anti-PD-1 agent.

- DLBCL: Participants must have received at least 2 prior systemic
chemo-immunotherapy regimens, including an anti-CD20 agent and
combination chemotherapy. Unless clinically contraindicated,
participants should have had disease that has relapsed after or be
refractory to intensive salvage chemotherapy, including autologous SCT.

- PTCL-NOS: Participants must have had at least 1 prior systemic therapy.
Participants must have received or have been ineligible to receive the
combination of cyclophosphamide, doxorubicin, vincristine, and
prednisone (CHOP) or CHOP-like therapy. Participants with CD30-positive
disease must have received or be ineligible to receive brentuximab
vedotin. Participants must have also received intensive salvage therapy
(defined as combination chemotherapy ± autologous SCT) unless they
refused or were deemed ineligible.

- Measurable disease defined as:

- Solid tumors: Measurable disease according to RECIST V1.1

- Lymphomas: Fluorodeoxyglucose (FDG)-avid disease by positron emission tomography
(PET) and measurable disease of ≥15 mm in the greatest transverse diameter by
computed tomography (CT) scan, as assessed by the site radiologist.

- A representative archival tumor tissue sample should be available as follows:
Participants must provide archived tumor tissue, if available, from the most recent
biopsy (≤12 months from screening). If archived tissue is not available, a fresh
baseline tumor biopsy will be requested for any participant enrolled in Part B whose
tumors are considered accessible and appropriate in the opinion of the investigator.

- ECOG Performance Status score of 0 or 1

Combination Inclusion Criteria (Part C)

- ECOG Performance Status score of 0 or 1

- NSCLC: histological or cytological confirmed metastatic disease. Participants must
have received no prior anti-PD-1/PD-L1 therapy allowed.

- HNSCC: histological or cytological confirmed metastatic disease. Participants must
have received no prior exposure to anti-PD-1/PD-L1 therapy.

- Cutaneous Melanoma: histological or cytological confirmed metastatic disease.
Participants must not have received anti-PD-1/PD-L1 targeted therapy.

- Measurable disease by CT or magnetic resonance imaging (MRI) as defined by RECIST V1.1

- Participants must provide archived tumor tissue, if available, from the most recent
biopsy (≤12 months from screening). If archived tissue is not available, a fresh
screening tumor biopsy will be requested for any participant whose tumors are
considered accessible and appropriate in the opinion of the investigator.

Monotherapy Exclusion Criteria (Parts A and B)

- History of another malignancy within 2 years before the first dose of study drug, or
any evidence of residual disease from a previously diagnosed malignancy. Exceptions
are malignancies with a negligible risk of metastasis or death.

- Chemotherapy, radiotherapy, biologics, and/or other antitumor treatment that has not
been completed before the first dose of study drug within the timeframe as follows:

- Chemotherapy, small molecule inhibitors, radiation, and/or other investigational
anticancer agents (excluding investigational monoclonal antibodies): 2 weeks

- Palliative radiotherapy (≤2 weeks of radiotherapy to non-central nervous
system [CNS] disease): ≤7 days prior to start of SEA-TGT

- Immune-checkpoint inhibitors: 4 weeks

- Monoclonal antibodies, antibody-drug conjugates, or radioimmunoconjugates: 4
weeks (2 weeks with documented disease progression)

- T-cell or other cell-based therapies: 12 weeks

- Known CNS metastases

- Participants with a history of CNS metastases are allowed if they have undergone
treatment for the CNS disease, symptoms have resolved, and steroids have been
discontinued.

- Leptomeningeal involvement by malignant disease is excluded regardless of prior
treatment.

- Previous allogeneic SCT. Participants with prior autologous SCT may be eligible if
they are >100 days from autologous SCT and fulfill all other inclusion criteria.

- Prior use of any anti-TIGIT mAb.

- Participants with a condition requiring systemic treatment with either corticosteroids
(>10 mg daily prednisone or equivalent) or other immunosuppressive medications within
14 days of enrollment. Inhaled or topical steroids and adrenal replacement steroid
doses >10 mg daily prednisone or equivalents are permitted in the absence of active
immune disease.

- Known hypersensitivity to any excipient contained in the drug formulation of SEA-TGT

Combination Exclusion Criteria (Part C)

- History of another malignancy within 2 years before the first dose of study drug, or
any evidence of residual disease from a previously diagnosed malignancy. Exceptions
are malignancies with a negligible risk of metastasis or death.

- Active, non-infectious pneumonitis, pulmonary fibrosis, or known history of immune
mediated pneumonitis.

- Previous therapy with an anti-PD-1 or anti-PD-L1 inhibitor.

- Chemotherapy, radiotherapy, biologics, and/or other antitumor treatment that has not
been completed before the first dose of study drug within the timeframe as follows:

- Chemotherapy, small molecule inhibitors, radiation, and/or other investigational
anticancer agents (excluding investigational monoclonal antibodies): 2 weeks

- Palliative radiotherapy (≤2 weeks of radiotherapy to non-CNS disease): ≤7
days prior to start of SEA-TGT.

- Immune-checkpoint inhibitors: 4 weeks

- Monoclonal antibodies, antibody-drug conjugates, or radioimmunoconjugates: 4
weeks (2 weeks with documented disease progression)

- T-cell or other cell-based therapies: 12 weeks

- Known active CNS metastases.

- Participants with a history of CNS metastases are allowed if they have undergone
treatment for the CNS disease, symptoms have resolved, and steroids have been
discontinued.

- Leptomeningeal involvement by malignant disease is excluded regardless of prior
treatment.

- Known hypersensitivity to any excipient contained in the drug formulation of SEA-TGT
or sasanlimab

- Participants with active known or suspected autoimmune disease or significant
autoimmune-related toxicity from prior immuno-oncology-based therapy (prior autoimmune
colitis, pneumonitis, transaminitis); Participants with vitiligo, controlled type 1
diabetes mellitus, residual hypothyroidism requiring hormone replacement, or
conditions not expected to recur in the absence of an external trigger are permitted
to enroll.

- History of interstitial lung disease

- Participants with a condition requiring systemic treatment with either corticosteroids
(>10 mg daily prednisone or equivalent) or other immunosuppressive medications within
14 days of enrollment. Inhaled or topical steroids and adrenal replacement steroid
doses >10 mg daily prednisone or equivalents are permitted in the absence of active
immune disease.

- Prior use of any anti-TIGIT mAb