The Company has acquired exclusive rights to develop patented rights, information rights and related know-how for OTIPRIO, OTIVIDEX and OTO-311 and potential future product candidates under licensing agreements with third parties. The licensing rights obligate the Company to make payments to the licensors for license fees, milestones and royalties. The Company is also responsible for patent prosecution costs, in the event such costs are incurred.

Under one of these agreements, the Company has achieved six development milestones and one regulatory milestone, totaling $2.8 million, related to its clinical trials for OTIPRIO, OTIVIDEX and OTO-311. The Company may be obligated to make additional milestone payments under the Company’s intellectual property license agreements as follows (in thousands):

Development	$	1,600
Regulatory		10,275
Commercialization		1,000
Total	$	12,875

In addition, the Company is obligated to pay royalties of less than five percent on net sales of OTIPRIO and on sales of any other commercial products developed using these licensed technologies. Such royalty expense for OTIPRIO is recorded to cost of product sales. The Company may also be obligated to pay to the licensors a percentage of fees received if and when the Company sublicenses the technology. As of March 31, 2019, the Company has not entered into any sublicense agreements for the licensed technologies.

The Company entered into an agreement related to OTIPRIO under which the Company is obligated to pay a one-time milestone payment of $0.5 million upon the first commercial sale of OTIPRIO and to pay royalties of less than one percent on net product sales of OTIPRIO. This milestone payment was paid during March 2016 and both this milestone payment and the royalties are recorded as selling, general and administrative expense. The royalties are payable until the later of: (i) the expiration of the last to expire patent owned by the Company in such country covering OTIPRIO; or (ii) 10 years after the first commercial sale of OTIPRIO after receipt of regulatory approval for OTIPRIO in such country.

During October 2014, the Company entered into an exclusive license agreement with Ipsen that enables the Company to use clinical and non-clinical gacyclidine data generated by Ipsen to support worldwide development and regulatory filings for OTO-313. Under this license agreement, the Company is obligated to pay Ipsen low single-digit royalties on annual net sales of OTO-313 by the Company or its affiliates or sublicensees, up to a maximum cumulative royalty totaling $10.0 million.