Many steps in the kallikrein-kinin pathway might be the potential target for COVID-19 treatment, like the blockade of tissue kallikrein activity, hence reducing the production of kinins or enhancing the kinin degradation by the use of recombinant active enzymes such as ACE2 or by blocking the bradykinin receptors B1 and B2. The gene discussed is KLK4; the disease is COVID-19.