Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS On February 23, 2022 (the “Closing Date”), we entered into a loan and security agreement (the “2022 Loan Agreement”) with SLR Investment Corp. as collateral agent (the “Agent”), and the lenders listed in the 2022 Loan Agreement (collectively the “2022 Lenders”). The 2022 Loan Agreement provides for a senior secured term loan facility, with $27.5 million (the “Term A Loan”) funded on the Closing Date and an additional $22.5 million that we may borrow on or prior to July 25, 2023; provided that (i) we have received approval by the FDA for our NDA for the control of serum phosphorus in chronic kidney disease patients on dialysis by December 31, 2022, and (ii) we have achieved certain product revenue milestone targets described in the 2022 Loan Agreement (the “Term B Loan”, and collectively, the Term A Loan and the Term B Loan, the “2022 Term Loan”). The 2022 Term A Loan funds are being used to repay the 2018 Term Loan with the Lenders as discussed in Note 6 - Borrowings and to fund our ongoing operations. We owed $25.0 million in principal payments from the 2018 Term Loan as of the Closing Date. The 2022 Term Loan has a maturity date of March 1, 2027. Borrowings under the 2022 Term Loan bear interest at a floating per annum rate equal to 7.95% plus the greater of (i) one tenth percent (0.10%) and (ii) one-month LIBOR. We are permitted to make interest-only payments on the 2022 Term Loan through March 31, 2024. Accordingly, beginning on April 1, 2024, we will be required to make monthly payments of interest plus repay the 2022 Term Loan in consecutive equal monthly installments of principal. We were obligated to pay $0.2 million, upon the closing of the Term A Loan, and we are obligated to pay $0.1 million on the earliest of (i) the funding date of the Term B Loan, (ii) July 25, 2023, and (iii) the prepayment, refinancing, substitution, or replacement of the Term A Loan on or prior to July 25, 2023. We are obligated to pay a fee equal to 4.95% of the aggregate original principal amount of the 2022 Term Loan funded upon the earliest to occur of the maturity date, the acceleration of the 2022 Term Loan, and the prepayment, refinancing, substitution, or replacement of the 2022 Term Loan. We may voluntarily prepay the outstanding 2022 Term Loan, subject to a prepayment premium of (i) 3% of the principal amount of the 2022 Term Loan if prepaid prior to or on the first anniversary of the Closing Date, (ii) 2% of the principal amount of the 2022 Term Loan if prepaid after the first anniversary of the Closing Date through and including the second anniversary of the Closing Date, or (iii) 1% of the principal amount of the 2022 Term Loan if prepaid after the second anniversary of the Closing Date and prior to the maturity date. The 2022 Term Loan is secured by substantially all of our assets, except for our intellectual property and certain other customary exclusions. Additionally, in connection with the 2022 Term Loan, we entered into an agreement, whereby we agreed to pay an exit fee in the amount 2% of the 2022 Term Loan funded (the “2022 Exit Fee”) upon (i) any change of control transaction or (ii) our achievement of net revenue from the sale of any products equal to or greater than $100.0 million, measured on a six (6) months basis, tested monthly at the end of each month. Notwithstanding the prepayment or termination of the 2022 Term Loan, the 2022 Exit Fee will expire 10 years from the Closing Date. The 2022 Loan Agreement contains customary representations and warranties and customary affirmative and negative covenants, including, among others, requirements as to financial reporting and insurance and restrictions on our ability to dispose of our business or property, to change our line of business, to liquidate or dissolve, to enter into any change in control transaction, to merge or consolidate with any other entity or to acquire all or substantially all the capital stock or property of another entity, to incur additional indebtedness, to incur liens on our property, to pay any dividends or other distributions on capital stock other than dividends payable solely in capital stock or to redeem capital stock. We have agreed to not allow our cash and cash equivalents to be less than the eighty percent (80%) of the outstanding 2022 Term Loan balance for any period in which our net revenue from the sale of any products, calculated on a trailing six (6) month basis and tested monthly, is less than sixty percent (60%) of the outstanding 2022 Term Loan balance. In addition, the 2022 Loan Agreement contains customary events of default that entitle the Agent to cause our indebtedness under the 2022 Loan Agreement to become immediately due and payable, and to exercise remedies against us and the collateral securing the 2022 Term Loan, including our cash. Under the 2022 Loan Agreement, an event of default will occur if, among other things, we fail to make payments under the 2022 Loan Agreement, we breach any of our covenants under the 2022 Loan Agreement, subject to specified cure periods with respect to certain breaches, certain Lenders determine that a material adverse change has occurred, we or our assets become subject to certain legal proceedings, such as bankruptcy proceedings, we are unable to pay our debts as they become due or we default on contracts with third parties which would permit the holder of indebtedness to accelerate the maturity of such indebtedness or that could have a material adverse change on us. Upon the occurrence and for the duration of an event of default, an additional default interest rate equal to 4% per annum will apply to all obligations owed under the 2022 Loan Agreement.