Kyowa Kirin International, formerly ProStrakan, is based in Galashiels.
KRN23 is the first of a pipeline of drugs from KKI's parent company, Kyowa Hakko Kirin, to reach the stage of seeking European approval.
The company said it was part of efforts to "contribute to the health and wellbeing of people around the world".
Rickets is caused by vitamin D deficiency resulting in weakened bones.
A Borders-based pharmaceuticals firm is seeking authorisation for a new drug for the treatment of the most common heritable form of rickets.