<p>One of the stages in pharmaceutical development is the creation of a design space that takes into account the relationship between critical process parameters (CPPs) and critical quality attributes (CQAs). The design space is determined using formal design of experiments. In particular, the design space can be developed and graphically depicted and the CPPs can be optimized by using three-level Box–Behnken designs and the surface response method. The present research studied the factors influencing the pharmaceutical and technological properties of a tablet mass during wet granulation in a high-speed mixer granulator for the further production of tablets with the active pharmaceutical ingredient (API) GSB-106, particularly the duration of the mixing process, the amount of moisturizing liquid, and the rotation speed of the mixer blades. Quadratic equations were calculated for characteristics such as flowability, Hausner index, and Carr coefficient using least-squares regression analysis. Two indicators, the amount of the dust fraction and the amount of the main fraction, were used to assess the granulometric characteristics. The factors having the greatest influence on the characteristics of the tablet mass were identified using variance analysis of the properties of the resulting compositions. A design space was constructed in the form of contour graphs of the correlation between the values of technological process factors and individual characteristics of the tablet mass to optimize the CPPs. The optimal solution to the problem was calculated using the Derringer–Suich generalized desirability function and converting all obtained and theoretically calculated values within the given ranges. A ranking of the desired pharmaceutical and technological characteristics was used to recalculate the values of partial desirabilities. The process conditions having the highest desirability were chosen after obtaining the five most optimal technological modes.</p>