Prior to the regulatory approval of our product candidates, we incur expenses for the manufacturing of drug product that could potentially be available to support the commercial launch of our products. Until the first reporting period when regulatory approval has been received or is otherwise considered probable, we record all such costs as research and development expense.

For TEGSEDI inventory related costs incurred subsequent to July 1, 2018, we reflected these amounts as inventory on our condensed consolidated balance sheets at the lower of cost or net realizable value under the first-in, first-out, or FIFO, basis. We periodically analyze our inventory levels and write down inventory that has become obsolete, inventory that has a cost basis in excess of its estimated realizable value and inventory in excess of expected sales requirements as cost of product sales. The determination of whether inventory costs will be realizable requires estimates by our management and if actual market conditions are less favorable than projected by our management, additional write-downs of inventory may be required which would be recorded as a cost of product sales in the condensed consolidated statements of operations. We did not record any material inventory write-offs for the six months ended June 30, 2019.

	June 30,		December 31,
	2019		2018
Raw materials	$	8,034	$	—
Work in process		192		—
Finished goods		60		85
Total inventories	$	8,286	$	85