Process for the preparation of high water affinity type products with controlled humidity

A process for preparing hygroscopic oligonucleotide product with controlled residual water content, comprising

• spray drying an aqueous solution of the hygroscopic oligonucleotide product in a spray drying equipment, and applying spray drying parameters as follows:
• Oligonucleotide concentration
• 5 to 25
• in feed solution (% w/w)
• Inlet N2 temperature (° C.)
• 180 to 220
• Outlet N2 temperature (° C.)
• 70 to 100
• Gas rate drying (heated N2
• 15 to 25
• flow rate in kg/h)
• Gas rate nozzle (N2 atomizing
• 0.8 to 1.5
• flow rate in kg/h)
• thereby obtaining a spray dried hygroscopic oligonucleotide product,
• wherein the spray drying parameters control residual water content of the spray dried ahygroscopic oligonucleotide product to a residual water content of 5% w/w to 15% w/w,
• wherein the hygroscopic oligonucleotide is 10 to 40 nucleotides in length,
• wherein the spray drying equipment comprises a spray chamber and an atomizer selected from a pressure drop-or a two fluid nozzle or from a rotary atomizer, and
• wherein the spray dried hygroscopic oligonucleotide product with controlled residual water content is free-flowing and easy to handle, compared to a spray dried hygroscopic oligonucleotide product without controlled residual water content.