Mirum prices $690M convertible notes, uses $475M cash + 3.2M shares to refinance $237M of 2029 debt

Mirum Pharmaceuticals, Inc. (“Mirum”) (Nasdaq: MIRM), a leading rare disease company, today announced the pricing of its offering of $600.0 million aggregate principal amount of 0.00% convertible senior notes due 2032 (the “notes”) in a private placement (the “offering”) to persons reasonably believed to be qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). The issuance and sale of the notes are scheduled to settle on May 15, 2026, subject to customary closing conditions. Mirum also granted the initial purchasers of the notes an option to purchase, for settlement within a period of 13 days from, and including, the date the notes are first issued, up to an additional $90.0 million aggregate principal amount of notes.

The initial conversion rate is 7.1971 shares of common stock per $1,000 principal amount of notes, which represents an initial conversion price of approximately $138.94 per share of common stock. The initial conversion price represents a premium of approximately 30.0% over the last reported sale price of $106.88 per share of Mirum’s common stock on May 12, 2026.

Mirum may not redeem the notes at its election at any time before June 6, 2029. The notes will be redeemable, in whole or in part (subject to a partial redemption limitation), for cash at Mirum’s option at any time, and from time to time, on a redemption date on or after June 6, 2029 and, in the case of any partial redemption, on or before the 30th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the notes to be redeemed, plus accrued and unpaid special interest and additional interest, if any, to, but excluding, the redemption date, but only if (i) the notes are “freely tradable” (as defined in the indenture for the notes) as of the date Mirum sends the related redemption notice and all accrued and unpaid additional interest, if any, has been paid in full as of the first interest payment date occurring on or before the date Mirum sends such notice; and (ii) the last reported sale price per share of Mirum’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date Mirum sends the related redemption notice; and (2) the trading day immediately before the date Mirum sends such notice.

Mirum estimates that the net proceeds from the offering will be approximately $583.8 million (or approximately $671.6 million if the initial purchasers fully exercise their option to purchase additional notes), after deducting the initial purchasers’ discounts and commissions and Mirum’s estimated offering expenses.

Mirum expects to use a portion of the net proceeds from the offering to pay the cash portion of the consideration in the note exchange transactions as described below. Mirum expects to use the remainder of the net proceeds of this offering for general corporate purposes, which may include the acquisition of complementary products, technologies, intellectual property or businesses as part of its growth strategy.

Mirum expects to use approximately $475.0 million of the net proceeds from the offering and to issue approximately 3.2 million shares of its common stock in exchange for approximately $237.2 million aggregate principal amount of the 4.00% convertible senior notes due 2029 (the “2029 notes”) in privately negotiated transactions (each, a “note exchange transaction”) entered into concurrently with the pricing of the offering.

In connection with any note exchange transaction, Mirum expects that holders of the 2029 notes who agree to have their 2029 notes exchanged and who have hedged their equity price risk with respect to such 2029 notes (the “hedged holders”) will, concurrently with, or shortly after, the pricing of the notes, unwind all or part of their hedge positions by buying Mirum’s common stock and/or entering into or unwinding various derivative transactions with respect to its common stock. The amount of Mirum’s common stock to be purchased by the hedged holders or the notional number of shares of Mirum’s common stock underlying such derivative transactions may be substantial in relation to the historical average daily trading volume of Mirum’s common stock. This activity by the hedged holders could increase (or reduce the size of any decrease in) the market price of Mirum’s common stock.

$600.0 million aggregate principal amount of convertible senior notes due 2032 (the “notes”) in a private placement (the “offering”) to persons reasonably believed to be qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). Mirum also expects to grant the initial purchasers of the notes an option to purchase, for settlement within a period of 13 days from, and including, the date the notes are first issued, up to an additional $90.0 million aggregate principal amount of notes.

Mirum expects to use a portion of the net proceeds from the offering to pay the cash portion of the consideration in the note exchange transactions as described below. Mirum expects to use the remainder of the net proceeds of this offering for general corporate purposes, which may include the acquisition of complementary products, technologies, intellectual property or businesses as part of its growth strategy.

Mirum expects to use a portion of the net proceeds from the offering and to issue shares of its common stock in exchange for a portion of its outstanding 4.00% convertible senior notes due 2029 (the “2029 notes”) in privately negotiated transactions (each, a “note exchange transaction”) entered into concurrently with the pricing of the offering. The terms of each note exchange transaction will depend on a variety of factors, including the market price of Mirum’s common stock and the trading price of the 2029 notes at the time of such note exchange transactions.

In connection with any note exchange transaction, Mirum expects that holders of the 2029 notes who agree to have their 2029 notes exchanged and who have hedged their equity price risk with respect to such 2029 notes (the “hedged holders”) will, concurrently with, or shortly after, the pricing of the notes, unwind all or part of their hedge positions by buying Mirum’s common stock and/or entering into or unwinding various derivative transactions with respect to its common stock. The amount of Mirum’s common stock to be purchased by the hedged holders or the notional number of

shares of Mirum’s common stock underlying such derivative transactions may be substantial in relation to the historical average daily trading volume of Mirum’s common stock. This activity by the hedged holders could increase (or reduce the size of any decrease in) the market price of Mirum’s common stock, including concurrently with the pricing of the notes, resulting in a higher effective conversion price for the notes.

On May 12, 2026, the Company issued a press release announcing the launch of the offering of the Notes. On May 12, 2026, the Company issued a press release announcing the pricing of the offering of the Notes.

The Notes were issued to the initial purchasers in reliance upon Section 4(a) (2) of the Securities Act of 1933, as amended (the “Securities Act”), in transactions not involving any public offering. The Notes were resold by the initial purchasers to persons whom the initial purchasers reasonably believe are “qualified institutional buyers,” as defined in, and in accordance with, Rule 144A under the Securities Act.

On May 15, 2026, Mirum Pharmaceuticals, Inc. (the “Company”) issued $690.0 million aggregate principal amount of its 0.00% Convertible Senior Notes due 2032 (the “Notes”), which includes the full exercise of the initial purchasers’ option to purchase up to an additional $90.0 million aggregate principal amount of Notes.

The Company may not redeem the Notes at its option at any time before June 6, 2029. The Notes will be redeemable, in whole or in part (subject to the “Partial Redemption Limitation” (as defined in the Indenture)), at the Company’s option at any time, and from time to time, on a redemption date on or after June 6, 2029 and, in the case of any partial redemption, on or before the 30th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the Notes to be redeemed, plus accrued and unpaid special interest and additional interest, if any, to, but excluding, the redemption date, but only if (i) the Notes are “Freely Tradeable” (as defined in the Indenture) as of the date the Company sends the related redemption notice and all accrued and unpaid additional interest, if any, has been paid in full as of the first interest payment date occurring on or before the date the Company sends such notice; and (ii) the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends such redemption notice; and (2) the trading day immediately before the date the Company sends such notice.

The Company estimates that the net proceeds from the offering of the Notes will be approximately $671.6 million after deducting the initial purchasers’ discounts and commissions and estimated offering expenses payable by the Company. The Company expects to use a portion of the net proceeds from the offering of the Notes to pay the cash portion of the consideration in the Note Exchange Transactions as described below. The Company expects to use the remainder of the net proceeds of this offering for general corporate purposes, which may include the acquisition of complementary products, technologies, intellectual property or businesses as part of its growth strategy.