DLT was defined as any of the following drug-related adverse events (AEs) occurring during the first cycle (21 days for IV dosing, 28 days for SC dosing) in Part 1: Grade 5 AE; Grade 4 neutropenia lasting >5 days from initiation of granulocyte colony stimulating factor; Grade 4 thrombocytopenia with bleeding; Platelet transfusion requirement or a platelet count <10,000/uL; Grade 4 non-hematologic AE; Grade 3 AE lasting >7 days despite optimal supportive care; Grade 3 central nervous system AE regardless of duration; met criteria for drug induced liver injury. Severity of AEs were graded according to Common Terminology Criteria for Adverse Events (CTCAE) v4.03. Grade 3 = severe AE. Grade 4 = life-threatening consequences; urgent intervention indicated. Grade 5 = death related to AE.

DLT analysis population included all enrolled participants who received at least 1 dose of study treatment and who did not have major treatment deviations during Cycle 1.

AE = any untoward medical occurrence in participant who received study treatment without regard to possibility of causal relationship. Treatment-emergent events = between first dose of study treatment and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. A serious adverse event (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. Grades of severity were defined by CTCAE v4.03. Grades of severity were defined by CTCAE v4.03. Grade 3 = severe AE. Grade 4 = life-threatening consequences; urgent intervention indicated. Grade 5 = death related to AE.

Analysis population included all enrolled participants who received at least 1 dose of study medication.

Treatment-related AE was any untoward medical occurrence attributed to study treatment in a participant who received study treatment. Treatment-emergent events = between first dose of study treatment and up to 28 days after last dose that were absent before treatment or that worsened relative to pretreatment state. An SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. Treatment-related AEs and SAEs were determined by the investigator. Grades of severity were defined by CTCAE v4.03. Grades of severity were defined by CTCAE v4.03. Grade 3 = severe AE. Grade 4 = life-threatening consequences; urgent intervention indicated. Grade 5 = death related to AE.

Analysis population included all enrolled participants who received at least 1 dose of study medication.

Following parameters were analyzed for laboratory examination: hematology (anemia, hemoglobin increased, lymphocyte count decreased, lymphocyte count increased, neutrophil count decreased, platelet count decreased, white blood cell decreased); chemistries (increase of alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, blood bilirubin, CPK, creatinine, gamma-glutamyl transferase [GGT], lipase, and serum amylase); urinalysis (proteinuria); coagulation (activated partial thromboplastin time prolonged, international normalized ratio [INR] increased). Grades of severity were defined by CTCAE v4.03. Grade 0 = No Change from normal or reference range (this grade is not included in the CTCAE v4.03 document but may used in certain circumstances). Grade 1 = mild adverse event (AE). Grade 2 = moderate AE; Grade 3 = severe AE. Grade 4 = life-threatening consequences; urgent intervention indicated. Grade 5 = death related to AE.

Analysis population included all enrolled participants who received at least 1 dose of study medication.

ORR was defined as percentage of participants with confirmed objective response (OR) of complete response (CR) and partial response (PR) based on RECIST version 1.1. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. All target nodes must decrease to normal size (short axis < 10 mm). All target lesions must be assessed. PR was defined as >= 30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. All target lesions must be assessed.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

ORR was defined as percentage of participants with objective response (OR) of complete response (CR) and partial response (PR) based on irRECIST. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. All target nodes must decrease to normal size (short axis < 10 mm). All target lesions must be assessed. PR was defined as >= 30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. All target lesions must be assessed.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

Cmax was the maximum concentration after dose administration observed directly from the data.

Analysis population included all enrolled participants treated who were evaluable for this outcome measure.

Area Under the Concentration Versus Time Curve (AUC) From Time Zero to the Last Quantifiable Time Point Prior to the Next Dose (AUClast) of PF-06801591 - Part 1

Analysis population included all enrolled participants treated who were evaluable for this outcome measure.

CL for IV dosing. CL was calculated by dose / AUCtau for Cycles 1 and 4 IV dosing. AUCtau was defined as area under the serum concentration time profile from time zero to time tau, the dosing interval, where tau = 504 hours for every 3 weeks (Q3W) IV dosing reporting arm.

Analysis population included all enrolled participants treated who were evaluable for this outcome measure.

Steady state volume of distribution of PF-0680159 for IV dosing. Vss was calculated by CL*MRT. CL was the clearance for IV dosing. MRT was the mean residence time calculated for a single IV dose as AUMCinf/AUCinf - (DOF/2). AUMCinf was the area under the moment curve from time 0 extrapolated to infinity. DOF was the duration of infusion. AUCinf was the area under the serum concentration time profile from time 0 extrapolated to infinity.

The PK parameter analysis population was defined as all enrolled participants in Part 1 who received study drug following IV administration and had sufficient information to estimate at least 1 of the pharmacokinetic (PK) parameters of interest. Number of participants analyzed represents the total number of participants in each treatment group in the PK parameter analysis population. Number analyzed represents the number of participants who had reportable parameter values of Vss.

Rac was calculated by (Cycle 4 AUCtau) / (Cycle 1 AUCtau). AUCtau was Area under the serum concentration time profile from time zero to time tau, the dosing interval, where tau = 504 hours for Q3W IV dosing and tau = 672 hours for every 4 weeks (Q4W) SC dosing.

Analysis population included all enrolled participants treated who were evaluable for this outcome measure.

t1/2 was calculated by Loge(2)/kel. kel was the terminal phase rate constant calculated by a linear regression of the log linear concentration time curve. Only those data points judged to describe the terminal log linear decline were used in the regression.

The PK parameter analysis population was defined as all enrolled participants in Part 1 who received study drug following IV or SC administration and had sufficient information to estimate at least 1 of the PK parameters of interest. Number of participants analyzed represents the total number of participants in each treatment group in the PK parameter analysis population. Number analyzed represents the number of participants who had reportable parameter values of t1/2.

Number of participants with ADA positive against PF-06801591 after IV and SC dosing - Part 1 and Part 2. A participant was ADA positive if (1) baseline titer was missing or negative and participant had ≥ 1 post-treatment positive titer (treatment-induced), or (2) positive titer at baseline and had a ≥ 0.602 in titer from baseline in ≥ 1 post-treatment sample (treatment-boosted). Participants who were ADA positive at baseline but did not become boosted post-treatment were considered as ADA negative.

Analysis population included all participants who received at least 1 dose of study treatment and had at least 1 post-treatment ADA result.

Number of participants with NAb positive against PF-06801591 after IV and SC dosing - Part 1 and Part 2. A participant was NAb positive if (1) baseline titer was missing or negative and participant had ≥ 1 post-treatment positive titer (treatment-induced), or (2) positive titer at baseline and had a ≥ 0.602 in titer from baseline in ≥ 1 post-treatment sample (treatment-boosted). Participants who were NAb positive at baseline but did not become boosted post-treatment were considered as NAb negative.

Analysis population included all participants who received at least 1 dose of study treatment and had at least 1 post-treatment ADA result. NAb-negative participants included participants who were ADA negative or ADA-positive participants who tested negative in the NAb assay.

PD-1 RO by sasanlimab was measured by the reduction of free receptor on the surface of CD8+ effector cells (CD3+, CD4-, CD8+, CD45RA+, CCR7-, CD279+) and CD8+ effector memory cells (CD3+, CD4-, CD8+, CD45RA-, CCR7-, CD279+) presented in pre- and postdose whole blood samples by flow cytometry. Percentage of baseline (ie, normalized change from baseline) PD-1 RO were calculated as [(percentage of cells at Cycle X Day X)/(percentage of cells at baseline)]*100, and are reported for this outcome measure. Baseline was defined as the most recent non-missing value prior to dosing.

Analysis population included all enrolled participants with at least 1 of the pharmacodynamic/biomarker parameters evaluated at pre- and/or post dose.

Number of participants achieving confirmed OR based on RECIST version 1.1 in Part 1. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. All target nodes must decrease to normal size (short axis < 10 mm). All target lesions must be assessed. PR was defined as >= 30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. All target lesions must be assessed.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

Number of participants achieving confirmed OR based on irRECIST in Part 1. OR = irCR + irPR. Overall immune related complete response (irCR) was defined as complete disappearance of all lesions (whether measurable or not) and no new lesions. All measurable lymph nodes also must have a reduction in short axis to <10 mm. Overall immune related partial response (irPR) was defined as sum of the diameters (longest for non nodal lesions, shortest for nodal lesions) of target and new measurable lesions decreases >=30%.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

PFS was defined as the time from initiation of study intervention to first documentation of tumor progression or to death due to any cause, whichever occurred first. PFS was analyzed by the Kaplan-Meier approach for each tumor type. As this outcome measure was a secondary endpoint defined in the protocol to investigate preliminary signal of efficacy, the results were analyzed and are reported for Part 1 dose-escalation groups combined to provide more statistically meaningful results, instead of results analyzed by dose level with very limited number of participants in each group.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

DOSD was analyzed by the Kaplan-Meier approach for each tumor type. Stable disease (SD) was defined as not qualifying for complete response (CR), partial response (PR), or progression. All target lesions must have been assessed. Stable could follow PR only in the rare case that the sum increased by less than 20% from the nadir, but enough that a previously documented 30% decrease no longer held. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. All target nodes must have decreased to normal size (short axis < 10 mm). All target lesions must have been assessed. PR was defined as greater than or equal to 30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. All target lesions must have been assessed.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

DOR was defined as the time from start date (which was the date of first documentation of PR or CR) to date of first documentation of objective progression or death. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. PR was defined as greater than or equal to 30% decrease under baseline of the sum of diameters of all target measurable lesions. Objective progression was defined as 20% increase in the sum of diameters of target measurable lesions above the smallest sum observed (over baseline if no decrease in the sum was observed during therapy), with a minimum absolute increase of 5 mm. As this outcome measure was a secondary endpoint defined in the protocol to investigate preliminary signal of efficacy, the results were analyzed and are reported for Part 1 dose-escalation groups combined to provide more statistically meaningful results, instead of results analyzed by dose level with very limited number of participants in each group.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death. DOR was only applicable to those participants with an objective response.

TTR was the time to confirmed or unconfirmed complete response (CR) or partial response (PR) based on investigator assessment per RECIST v1.1 by tumor type. CR was defined as complete disappearance of all target lesions with the exception of nodal disease. All target nodes must have decreased to normal size (short axis < 10 mm). All target lesions must have been assessed. PR was defined as greater than or equal to 30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter was used in the sum for target nodes, while the longest diameter was used in the sum for all other target lesions. All target lesions must have been assessed.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

TTP was the time to objective progression. Objective progression was defined as 20% increase in the sum of diameters of target measurable lesions above the smallest sum observed (over baseline if no decrease in the sum was observed during therapy), with a minimum absolute increase of 5 mm. TTP was analyzed by the Kaplan-Meier approach for each tumor type.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

Median time to death was analyzed by the Kaplan-Meier approach for each tumor type.

Analysis population included all the randomized participants who received at least 1 dose of study medication, had measurable disease baseline assessment (within 28 days prior to study entry) and at least 1 post baseline assessment or disease progression, global deterioration of health status, or death.

Probability of survival was calculated from the product-limit method.

Analysis population included all the randomized participants who received PF-06801591 and had at least 1 post-dose concentration measurement above the lower limit of quantification (LLQ).

Trough PF-06801591 Concentrations (Ctrough) - Part 2. Ctrough was directly observed from data.

Analysis population included all participants who received PF-06801591, had no protocol deviations affecting the pharmacokinetics (PK) assessment, and had at least 1 post-dose concentration measurement above lower limit of quantification.