Cocoon Biotech recently filed an amendment to an SEC Form D to reveal that it sold more than $4 million in a debt offering.

The Cambridge, Mass.–based company filed the Form D/A last week to confirm the sale of nearly $4.5 million on an offering that had its first sale on Feb. 15, 2017.

According to the amendment, Cocoon Biotech does not intend for the offering to last for more than a year. The company set a minimum investment for outside investors at $5,000 and listed the total offering amount as indefinite.

Cocoon listed 32 investors who have already contributed to the debt offering in the amendment. The biotech company is developing a silk fibroin as a material science platform that it believes offers the potential to change the ability to formulate, deliver and stabilize molecules.

Earlier this year, Cocoon and Decibel Therapeutics announced a plan to work together and research drug formulations optimized for transtympanic delivery to the ear. The deal centered around Cocoon’s silk fibroin platform, for which the company was slated to receive an upfront license fee, development milestone payments and downstream royalties for each licensed program.