• Written informed consent and HIPAA authorization for release of personal health information prior to registration. NOTE: HIPAA authorization may be included in the informed consent or obtained separately.

• Male and female, age ≥ 18 years at the time of consent.

• ECOG Performance Status of 0-1 within 28 days prior to registration.

• Histological or cytological evidence of Merkel cell cancer per AJCC, 8th edition.

• Presence of somatostatin receptors by Ga-68 dotatate (or equivalent) imaging, which is a requirement for PRRT (lutetium Lu 177 dotatate \[Lutathera®\]). Must have at least one measurable lesion per RECIST 1.1.

• Must have progressed on treatment with an anti-PD-1/L1 mAb administered either as monotherapy or in combination with other checkpoint inhibitors or other therapies. PD-1 treatment progression is defined by meeting all of the following criteria:

‣ Has received at least 2 doses of an approved anti-PD-1/L1 mAb

⁃ Has demonstrated disease progression after anti-PD-1/L1 as defined by RECIST v1.1.

⁃ Progressive disease has been documented within 12 weeks from the last dose of anti-PD-1/L1 mAb. Note: This determination is made by the local investigator. Once disease progression is confirmed, the initial date of disease progression documentation will be considered the date of disease progression.

• Prior cancer treatment must be completed and the subject must have recovered from all reversible acute toxic effects of the regimen (other than alopecia) to Grade ≤ 1 or baseline.

• Demonstrate adequate organ function as defined in the table below. All screening labs to be obtained within 28 days prior to registration.

‣ Hematological:

• Absolute Neutrophil Count (ANC): ≥ 1500/uL

∙ Platelets: ≥100,000/uL

∙ Hemoglobin (Hgb): ≥9.0g/dL or ≥5.6mmol/L

⁃ Renal:

• Creatinine: 1.5 x ULN OR

∙ Measured or calculated creatinine clearance (GFR can also be used in place of creatinine or CrCl): ≥30mL/min for participant with creatinine levels \>1.5 x institutional ULN

⁃ Hepatic:

∙ --Total bilirubin: ≤1.5 x ULN OR direct bilirubin ≤ULN for participants with total bilirubin levels \>1.5 x ULN

⁃ AST(SGOT) and ALT(SGPT): ≤2.5 x ULN (≤5 x ULN for participants with liver metastases)

⁃ Coagulation:

• International normalized ratio (INR) OR prothrombin time (PT): ≤1.5 × ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulants

∙ Activated partial thromboplastin time (aPTT): ≤1.5 × ULN unless participant is receiving anticoagulant therapy as long as PT or aPTT is within therapeutic range of intended use of anticoagulants

• Females of childbearing potential who are sexually active with a male able to father a child must have a negative serum pregnancy test within 7 days prior to registration.

⁃ Females of childbearing potential who are sexually active with a male able to father a child must be willing to abstain from heterosexual activity or to use an effective method(s) of contraception from the time of informed consent, during the study and for 7 months after the last dose of study drug(s). Males able to father a child who are sexually active with female of childbearing potential must be willing to abstain from heterosexual activity or to use an effective method(s) of contraception from initiation of treatment, during the study and for 120 days after the last dose of study drug(s).

⁃ Participants who are HBsAg positive are eligible if they have received HBV anti-viral therapy for at least 4 weeks and have undetectable HBV viral load prior to registration.

⁃ Note: Participants should remain on anti-viral therapy throughout study intervention and follow local guidelines for HBV anti-viral therapy post completion of study intervention.

⁃ Hepatitis B screening tests are not required unless:

‣ Known history of HBV infection

‣ As mandated by local health authority

⁃ Participants with a history of HCV infection are eligible if HCV viral load is undetectable at screening.

⁃ Note: Participants must have completed curative anti-viral therapy at least 4 weeks prior to randomization.

⁃ Hepatitis C screening tests are not required unless:

‣ Known history of HCV infection

‣ As mandated by local health authority

⁃ HIV-infected participants must have well-controlled HIV on anti-retroviral therapy (ART), defined as:

• Participants on ART must have a CD4+ T-cell count ≥350 cells/mm3 at the time of screening

∙ Participants on ART must have achieved and maintained virologic suppression defined as confirmed HIV RNA level below 50 or the LLOQ (below the limit of detection) using the locally available assay at the time of screening and for at least 12 weeks before screening

∙ It is advised that participants must not have had any AIDS-defining opportunistic infections within the past 12 months.

∙ Participants on ART must have been on a stable regimen, without changes in drugs or dose modification, for at least 4 weeks before study entry (Day 1) and agree to continue ART throughout the study NOTE: HIV-infected participants with a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease are excluded.

⁃ As determined by the enrolling physician or protocol designee, ability of the subject to understand and comply with study procedures for the entire length of the study.