Convertible Senior Notes Due 2022 (“2022 Notes”)
We fully redeemed the $35 million remaining principal amount of the 2022 Notes plus accrued interest by delivering cash upon maturity on May 1, 2022. The effective interest rate for the 2022 Notes was 4.8%. For the three- and six month periods ended June 30, 2022, total interest expense related to the 2022 Notes was $0.1 million and $0.6 million, respectively, primarily from coupon interest expense. For the three- and six-month periods ended June 30, 2021, total interest expense related to the 2022 Notes was $0.4 million and $0.8 million, respectively, with coupon interest expense of $0.4 million and $0.7 million, respectively, and the amortization of issuance costs of $0.1 million for the six-month period ended June 30, 2021.
Convertible Senior Notes Due 2023 (“2023 Notes”)
The 2023 Notes bear interest at a coupon interest rate of 4.125% per annum payable semi-annually in arrears on March 15 and September 15 of each year until maturity. The 2023 Notes mature on September 15, 2023 unless earlier converted, redeemed or repurchased by us. The 2023 Notes are convertible by their holders at any time beginning March 15, 2023 at an initial conversion rate of 105.6133 shares of our common stock per $1,000 principal amount, which currently represents 3,168,399 potentially convertible shares at an initial conversion price of approximately $9.47 per share of common stock. Upon conversion, we have the right to satisfy our conversion obligation by delivering cash, shares of our common stock or any combination thereof.
Prior to March 15, 2023, holders of the 2023 Notes may convert their notes if the closing price of our common stock exceeds 130% of the conversion price for at least 20 days in the period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter (share price condition) or if the trading price of the 2023 Notes is equal to or less than 97% of the conversion value of the notes during the 5 consecutive business days immediately after any 10 consecutive trading day period (trading price condition). Holders of the 2023 Notes may also convert their notes if we make certain distributions on shares of our common stock or engage in certain corporate transactions, in which case the holders may be entitled to an increase in the conversion rate, depending on the price of our common shares and the time remaining to maturity, of up to 47.5260 shares of our common stock per $1,000 principal amount.
Prior to March 15, 2021, the 2023 Notes were not redeemable. On or after March 15, 2021, we may redeem all or any portion of the 2023 Notes if the price of our common stock has been at least 130% of the conversion price for at least 20 trading days during any 30 consecutive trading day period preceding our redemption notice. Any redemption would be payable in cash equal to 100% of the principal amount to be redeemed plus accrued and unpaid interest and a “make-whole premium” calculated as the present value of all remaining scheduled interest payments. Holders of the 2023 Notes may convert any of their notes if we call the notes for redemption. Holders of the 2023 Notes may also require us to repurchase the notes following a “fundamental change,” which includes a change of control or a termination of trading of our common stock (as defined in the indenture governing the 2023 Notes).
The indenture governing the 2023 Notes contains customary terms and covenants, including that upon certain events of default, the entire principal amount of and any accrued interest on the notes may be declared immediately due and payable. In the case of certain events of bankruptcy, insolvency or reorganization relating to us or a significant subsidiary, the principal amount of the 2023 Notes together with any accrued interest will become immediately due and payable.
The effective interest rate for the 2023 Notes is 4.8%. For the three- and six-month periods ended June 30, 2022, total interest expense related to the 2023 Notes was $0.3 million and $0.7 million, respectively, with coupon interest expense of $0.3 million and $0.6 million, respectively, and the amortization of debt issuance costs of $0.1 million for the six-month period ended June 30, 2022. For the three- and six-month periods ended June 30, 2021, total interest expense related to the 2023 Notes was $0.3 million and $0.7 million, respectively, with coupon interest expense of $0.3 million and $0.6 million, respectively, and the amortization of issuance costs of $0.1 million for the six-month period ended June 30, 2021.