A Phase I Comparative Study of Pharmacokinetics, Safety, and Efficacy of RPH-002 and Erbitux® in Unresectable Metastatic or Recurrent Head and Neck Squamous Cell Carcinoma

This study is a multicenter, open-label, randomized Phase I study

This clinical study includes the following stages:

* Stage 1: Evaluation of the pharmacokinetics of drugs RPH-002 and Erbitux® after the first administration, and evaluation of the safety and immunogenicity of drugs RPH-002 and Erbitux® after four administrations of the study therapy * Stage 2: Evaluation of pharmacokinetics, safety, immunogenicity, and pilot efficacy of drugs RPH-002 and Erbitux® during up to 18 weeks of therapy * Stage 3: Evaluation of safety, immunogenicity, and pilot efficacy of RPH-002 and Erbitux® after 6 months of therapy, as well as evaluation of safety, immunogenicity, and pilot efficacy of drug RPH-002 after 1 year of therapy

Therapy with cetuximab within this clinical study will continue until disease progression or the development of unacceptable toxicity

Disease progression is defined as the presence of one or more of the following criteria:

* Clinical progression as assessed by the investigator * Radiologically confirmed progression according to RECIST 1.1 criteria: an increase of at least 20% in the sum of diameters of target lesions compared with the smallest sum recorded during the study (with an absolute increase of at least 5 mm), or the appearance of one or more new lesions

The maximum duration of therapy with cetuximab within the study will be 54 weeks

The study will include the following periods:

1. Screening Period 1 (up to 15 days)

Includes Days -14 to 0 (prior to the first administration of the investigational product/comparator) 2. Main Period (Period 1)

The main study period includes Days 1-126

Patients will be randomized in a 1:1 ratio into one of two study groups: RPH-002 and Erbitux®. Patients will receive combination therapy with RPH-002 or Erbitux®, docetaxel, and cisplatin for 18 weeks, or until the development of unacceptable toxicity or disease progression

The Main Period includes collection of data on complaints and symptoms, physical examination, assessment of vital signs (body temperature, blood pressure, pulse), monitoring of laboratory parameters (hematology, serum biochemistry, coagulation tests, blood analysis, and urinalysis), blood sampling for determination of serum cetuximab concentration and immunogenicity assessment, ECG, and evaluation of Karnofsky performance status. Tumor response assessment will be performed every 6 weeks during Period 1 3. Screening Period 2 (up to 8 days)