Aldexa Therapeutics, a clinical-stage biotech developing treatments for rare skin and eye diseases, filed on Monday with the SEC to raise up to $20 million in an initial public offering. The Burlington, MA-based company, which was founded in 2004, plans to list on the NASDAQ under the symbol ALDX. Aldexa Therapeutics initially filed confidentially on December 4, 2013. Aegis Capital is the sole bookrunner on the deal. No pricing terms were disclosed.