Inclusion Criteria:

          1. Recurrent or metastatic HNSCC (oral cavity, oropharynx, larynx, hypopharynx) and not
             amenable to local therapy with curative intent (surgery or radiation therapy)

          2. Qualifies for Pembrolizumab monotherapy as part of standard of care (has PD-L1 CPS ≥1)

          3. ECOG performance status of 0-1

          4. Measurable disease by RECIST 1.1

          5. Be > 18 years of age on day of signing informed consent

          6. Be willing and able to provide written informed consent for the trial

          7. Life expectancy of at least 12 weeks based on investigator estimate

          8. Adequate organ function as defined as:

               -  WBC ≥ 2000/μL

               -  Neutrophils ≥ 1500/μL

               -  Platelets ≥ 100 x103/μL

               -  Hemoglobin ≥ 8.0 g/dL

               -  serum creatinine < 1.5 x ULN or creatinine clearance (CrCl) > 40 mL/min (using
                  the Cockcroft-Gault formula)

               -  AST/ALT < 3 x ULN

               -  Total bilirubin < 1.5 x ULN (except subjects with Gilbert Syndrome who can have
                  total bilirubin < 3mg/dL.

          9. Women of childbearing potential (WCBP) must have a negative urine pregnancy test
             within 7 days prior to the first study intervention.

         10. WCBP and men must agree to use adequate contraception (hormonal or barrier method of
             birth control; abstinence) prior to study entry and through 120 days after the last
             dose of study treatment. Should a woman become pregnant or suspect she is pregnant
             while she or her partner is participating in this study, she should inform her
             treating physician immediately. Men treated or enrolled on this protocol must also
             agree to use adequate contraception prior to the study and for the duration of study
             participation.

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        Exclusion Criteria:

          1. Patients with salivary gland SCC or cutaneous SCC will be excluded

          2. Has received systemic therapy (chemotherapy, immunotherapy, investigational therapy)
             for the treatment of recurrent/metastatic disease. Systemic therapy given concurrent
             with radiation treatment in the recurrent setting does not exclude the patient.

          3. Untreated brain metastasis or leptomeningeal metastasis.

          4. Tumor invades into the internal carotid artery or other major blood vessels whereby
             the treating investigator feels anti-coagulation is contraindicated.

          5. Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy
             (Prednisone > 10mg or equivalent) or any other form of immunosuppressive therapy
             within 7 days prior to the first dose of trial treatment.

          6. Has an active autoimmune disease requiring systemic treatment within the past 3 months
             or a documented history of clinically severe autoimmune disease, or a syndrome that
             requires systemic steroids or immunosuppressive agents. Subjects with vitiligo,
             Grave's disease, or psoriasis not requiring systemic therapy or resolved childhood
             asthma/atopy would be an exception to this rule. Subjects that require use of
             bronchodilators or local steroid injections would not be excluded from the study.
             Subjects with hypothyroidism stable on hormone replacement or Sjogren's syndrome will
             not be excluded from the study.

          7. Has a history of non-infectious pneumonitis that required steroids, evidence of
             interstitial lung disease, or currently active non-infectious pneumonitis.

          8. Has an active infection requiring systemic therapy.

          9. Has a history or current evidence of any condition, therapy, or laboratory abnormality
             that might confound the results of the trial, interfere with the subject's
             participation for the full duration of the trial, or is not in the best interest of
             the subject to participate, in the opinion of the treating investigator.

         10. Is pregnant or breastfeeding or expecting to conceive or father children within the
             projected duration of the trial, starting with the screening visit through 120 days
             after the last dose of trial treatment.

         11. Has received prior therapy with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or
             anti-Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) antibody (including
             ipilimumab or any other antibody or drug specifically targeting T-cell co-stimulation
             or checkpoint pathways) in the recurrent/metastatic setting. Patients that received
             any of these agents in the upfront curative intent setting can be enrolled as long as
             it has been 1 year since the last dose.

         12. Has a known history of Human Immunodeficiency Virus (HIV) (HIV 1/2 antibodies).

         13. Has known active Hepatitis B or active Hepatitis C

         14. Has received a live vaccine within 30 days prior to the first dose of trial treatment.

         15. Concurrent therapy with an angiotensin-converting enzyme (ACE) inhibitor. ACE
             inhibitors must be discontinued at least 14 days prior to initiation of each
             Hemopurifier treatment and remain discontinued for 24 hours post treatment.

         16. Systolic blood pressure less than 100 on at least 2 readings

         17. Subjects with electro-cardiograms (ECG) showing clinically significant abnormalities.

         18. Recent history of bleeding or bleeding disorders or any condition whereby in the
             opinion of the treating investigator giving anti-coagulation during the Hemopurifier
             treatment would be contraindicated

         19. Any disorder or condition that in the opinion of the treating investigator would not
             be able to tolerate dialysis catheter placement, blood volume losses during
             Hemopurifier treatment or research blood draws.

         20. History of heparin allergy or heparin induced thrombocytopenia.

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