Biosimilars are biological agents that are highly analogous to their reference products currently approved and licensed by the U.S. Food and Drug Administration (FDA). Biosimilars possess no differences in their safety, purity, potency, or effectiveness compared to their respective reference biologic agents. The abbreviated licensure pathway 351(k) for biosimilars or agents interchangeable with FDA-approved biological agents (reference product) was formed by Congress by The Biologics Price Competition and Innovation Act (BPCI Act) of 2009. Biosimilars aim to increase the number of biologics available at more inexpensive costs when compared to their reference products, further increasing patient access to more treatment options. Similar to biologics or reference products, biosimilars are expected to meet the FDA's meticulous approval criteria, ensuring the reliability of the agent's safety, efficacy, quality, and effectiveness. The FDA approval process for biosimilars is based on data proving its prominent similarity and correlation to an already FDA-approved biologic agent (reference product) and its indications for use. No clinically meaningful differences among the biosimilar and its respective reference agent should exist. Differences exist in the regulatory provisions for the original biologic agent (reference product) and a biosimilar as the biosimilars obtain approval from FDA by their abbreviated approval pathway. Biosimilars seeking FDA approval must include data assessments demonstrating the agent's similarity to a reference product acquired from analytical investigations, animal studies, and clinical studies. Added data and analyses of the biosimilars immunogenicity, pharmacokinetics, pharmacodynamics, and data discussing the indication(s) the reference product is licensed and approved for use are also included. To date, ten biological agents: bevacizumab, etanercept, epoetin-alfa, trastuzumab, adalimumab, pegfilgrastim, filgrastim, infliximab, rituximab, and insulin glargine, have been used as reference products for the approval of 30 biosimilar agents. Biosimilars can be used in the management of various inflammatory and autoimmune diseases. Ailments such as rheumatoid arthritis (RA), polyarticular juvenile idiopathic arthritis (JIA), psoriatic arthritis (PA), ankylosing spondylitis (AS), plaque psoriasis (PsO), inflammatory bowel disease (IBD): adult Crohn disease (CD), ulcerative colitis (UC), granulomatosis with polyangiitis (GPA) (Wegener granulomatosis), microscopic polyangiitis (MPA), and type 1 diabetes mellitus (DM). Filgrastim-sndz, a biosimilar of the reference product "filgrastim," was the first-ever biosimilar to receive FDA approval in March 2015 and is characterized as a leukocyte growth factor indicated to reduce infections caused by febrile neutropenia in the neutropenic and immunosuppressed subjects. Other indications of biosimilars alongside inflammatory diseases include management for specific malignancies and secondary causes of anemia. In September 2017, bevacizumab-awwb was the first biosimilar that was granted FDA approval for certain cancers. A few months later, in December 2017, biosimilar trastuzumab-dkst was also granted FDA approval for specific malignancies. Cancers indicative of biosimilar therapy include non-squamous non-small cell lung cancer, metastatic colorectal cancer, metastatic renal cell carcinoma, glioblastoma, recurrent or metastatic cervical cancer, HER2 (human epidermal growth factor receptor 2) associated breast cancer, and HER2 associated gastric (metastatic) or gastroesophageal junction adenocarcinoma, chronic lymphocytic leukemia (CLL), non-Hodgkin lymphoma (NHL). To date, new biosimilars are currently still being FDA approved, with the latest approval coming on July 28, 2021, for biosimilar agent insulin glargine-yfgn, a long-acting insulin agent indicated for pediatric type 1 diabetes mellitus (DM) and adult patients with DM type 1 and DM type 2. Biosimilars agent insulin glargine-yfgn is the first insulin biosimilar agent to receive FDA approval and is also the first interchangeable agent in the class of biosimilar agents. Interchangeable products are biosimilars that meet additional criteria specified by the Biologics Price Competition and Innovation Act during the assessment and testing of the agent during its FDA approval process. Data is required demonstrating clinical results as its respective reference product in any subject treated with the interchangeable products. Data on the interchangeable products substituted with their reference product in terms of safety and efficacy of alternating back and forth have been assessed and evaluated by the FDA prior to their approval. Once an interchangeable product has been approved, it may be interchanged for their reference product without requiring additional consulting from the prescribing clinician or healthcare professional. Table 1: Summarizes all FDA approved biosimilars