https://www.selleckchem.com/products/1-naphthyl-pp1-hydrochloride.html Bromelain, papain and chymotrypsin are proteolytic enzymes. They can be found in fruits such as pineapple or papaya, but also in the human body, namely in the pancreas. Besides their enzymatic function, they are said to reduce side-effects and even to improve the outcome of cancer therapies. We, therefore, aimed to critically examine and systematically review existing evidence on the role that these enzymes might play in cancer treatment. In May 2019, a systematic literature search was conducted by using five electronic databases (Embase, Cochrane, PsychInfo, CINAHL and Medline) to find studies concerning the use, effectiveness and potential harm of enzyme therapy on cancer patients. Out of 13,046 search results, 15 studies with 3,008 patients were included in this systematic review. Patients treated with enzymes were diagnosed with various entities of gastrointestinal, gynecologic, head and neck and lung cancer as well as hematological malignancies. The therapy concepts included mainly oral intake of enzymes in addition to conventional therapies. Investigated outcomes were side-effects of anticancer therapy, quality of life, as well as anticancer effects and survival rates. In summary, due to conflicting results and moderate quality of the included studies, the evidence is insufficient to attribute positive effects to enzymes in terms of better tolerability of the various antineoplastic therapies or even improvement in treatment efficacy. In most cases, enzyme therapy was well tolerated; side-effects were mainly gastrointestinal complaints such as diarrhea or meteorism. On the basis of existing evidence, there is no clear therapeutic benefit of enzymes neither as supportive therapy nor as part of antineoplastic therapy. On the basis of existing evidence, there is no clear therapeutic benefit of enzymes neither as supportive therapy nor as part of antineoplastic therapy. Human telomerase reverse