This study will also include a comparative assessment of immunogenicity, pharmacodynamic parameters and a pilot evaluation of RPH-075 efficacy. conditions: Skin Melanoma conditions: Squamous Non-small-cell Lung Cancer conditions: Head and Neck Squamous Cell Carcinoma studyType: INTERVENTIONAL phases: PHASE1 allocation: RANDOMIZED interventionModel: PARALLEL primaryPurpose: TREATMENT masking: DOUBLE whoMasked: PARTICIPANT whoMasked: INVESTIGATOR count: 90 type: ACTUAL name: RPH-075 name: Keytruda® measure: Area under the curve "concentration-time" (AUC(0-504)) of pembrolizumab measure: Incidence of Adverse Reactions (ARs) measure: Maximum Plasma Concentration (Cmax) of pembrolizumab measure: Maximum serum concentration of pembrolizumab at steady state (Сmax ss) measure: Minimal serum concentration of pembrolizumab at steady state (Сmin ss) measure: Area under the curve "concentration-time" of pembrolizumab at steady state (AUCtau ss) measure: Incidence of Treatment-Emergent Adverse Events (AEs) measure: Incidence of Immune-mediated adverse reactions (imARs) measure: Incidence of Treatment-Emergent AEs with grade 3 or more measure: Incidence of Treatment-Emergent ARs with grade 3 or more measure: Incidence of imARs with grade 3 or more measure: Incidence of serious adverse events (SAEs) measure: Incidence of serious adverse reactions (SARs) measure: The proportion of patients (%) who required therapy discontinuation due to AR development measure: The proportion of patients (%) who developed binding antibodies and neutralizing antibodies to pembrolizumab sex: ALL minimumAge: 18 Years stdAges: ADULT stdAges: OLDER_ADULT facility: State Budgetary Healthcare Institution of the city of Moscow "Moscow City Oncological Hospital No. 62 of the Department of Health of the City of Moscow" city: Istra state: Moscow Region zip: 143423 country: Russian Federation lat: 55.91997 lon: 36.86867 facility: "New Clinic" LLC city: Pyatigorsk state: Stavropol Territory zip: 357500 country: Russian Federation lat: 44.04861 lon: 43.05944 facility: Regional State Budgetary Healthcare Institution "Altai Regional Oncological Dispensary" city: Barnaul state: The Altai Republic zip: 656045 country: Russian Federation lat: 53.36056 lon: 83.76361 facility: Autonomous Institution of the Chuvash Republic "Republican Clinical Oncological Dispensary" of the Ministry of Health of the Chuvash Republic city: Cheboksary state: The Chuvash Republic zip: 428020 country: Russian Federation lat: 56.13222 lon: 47.25194 facility: State Autonomous Healthcare Institution Republican Clinical Oncological Dispensary of the Ministry of Health of the Republic of Bashkortostan city: Ufa state: The Republic Of Bashkortostan zip: 450054 country: Russian Federation lat: 54.74306 lon: 55.96779 facility: State Budgetary Healthcare Institution of the Arkhangelsk region "Arkhangelsk Clinical Oncological Dispensary" city: Arkhangelsk zip: 163045 country: Russian Federation lat: 64.5401 lon: 40.5433 facility: Regional budgetary healthcare institution "Ivanovo Regional Oncological Dispensary" city: Ivanovo zip: 153040 country: Russian Federation lat: 56.99719 lon: 40.97139 facility: State Budgetary healthcare Institution "Kuzbass Clinical Oncological Dispensary named after M.S. Rappoport" city: Kemerovo zip: 650036 country: Russian Federation lat: 55.33333 lon: 86.08333 facility: State Budgetary Healthcare Institution of the city of Moscow "City Clinical Oncological Hospital No. 1 of the Department of Health of the City of Moscow" city: Moscow zip: 105005 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: State Budgetary Institution of Healthcare of the city of Moscow "Moscow Clinical Scientific and Practical Center named after A.S. Loginov of the Department of Healthcare of the City of Moscow" city: Moscow zip: 111123 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: Federal State Budgetary Institution "N.N. Blokhin National Medical Research Center of Oncology" of the Ministry of Health of the Russian Federation city: Moscow zip: 115478 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: Federal State Budgetary Scientific Institution "Russian Scientific Center of Surgery named after Academician B.V. Petrovsky" city: Moscow zip: 119435 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: Federal State Autonomous Educational Institution of Higher Education I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University) city: Moscow zip: 119991 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: Medsi Group of Companies JSC city: Moscow zip: 123056 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: "Research lab" LLC city: Moscow zip: 127521 country: Russian Federation lat: 55.75222 lon: 37.61556 facility: State Budgetary Healthcare Institution of the Perm Territory "Perm Regional Oncological Dispensary" city: Perm zip: 614066 country: Russian Federation lat: 58.01046 lon: 56.25017 facility: State Budgetary Healthcare Institution Leningrad Regional Clinical Hospital city: Saint Petersburg zip: 188300 country: Russian Federation lat: 59.93863 lon: 30.31413 facility: Private healthcare institution "Clinical Hospital "Russian Railways-Medicine" of the city of St. Petersburg" city: Saint Petersburg zip: 195271 country: Russian Federation lat: 59.93863 lon: 30.31413 facility: "Av Medical Group" LLC city: Saint Petersburg zip: 196006 country: Russian Federation lat: 59.93863 lon: 30.31413 facility: St. Petersburg State Budgetary Healthcare Institution "City Clinical Oncological Dispensary" city: Saint Petersburg zip: 197022 country: Russian Federation lat: 59.93863 lon: 30.31413 facility: Federal State Budgetary Institution "N.N. Petrov National Medical Research Center of Oncology" of the Ministry of Health of the Russian Federation city: Saint Petersburg zip: 197758 country: Russian Federation lat: 59.93863 lon: 30.31413 facility: State Budgetary Healthcare Institution "Samara Regional Clinical Oncological Dispensary" city: Samara zip: 443031 country: Russian Federation lat: 53.20007 lon: 50.15 facility: The State Autonomous healthcare Institution of the Tyumen region "Multidisciplinary clinical Medical Center "Medical City" city: Tyumen zip: 625041 country: Russian Federation lat: 57.15222 lon: 65.52722 hasResults: False