4. Fair Value of Financial Instruments

Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. In order to increase consistency and comparability of fair value measurements, financial instruments are categorized based on a hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three broad levels, which are described below:

The Company’s financial assets and liabilities that are measured at fair value on a recurring basis consist of money market funds, deferred compensation plan liabilities, contingent consideration liabilities and equity investments. The Company invests excess cash from its operating cash accounts in overnight investments and reflects these amounts in cash and cash equivalents in the condensed consolidated balance sheets at fair value using quoted prices in active markets for identical assets. Investment in equity securities resulting from the Perspective Therapeutics, Inc. (“Perspective”) and Radiopharm Theranostics Limited (“Radiopharm”) strategic agreements were recorded at fair value by the Company and are adjusted for price changes observable in the market each quarter. The Company measured the Series E-1 convertible Preferred Stock of Illuminated, acquired in April 2026 upon conversion of the Installment Note at their initial fair value, with subsequent carrying value adjustments recorded for impairment and observable price changes. See the section entitled ”Installment Note” below for more information about this transaction. The Company recorded the contingent consideration liabilities resulting from the acquisitions of Evergreen and Lantheus Biosciences at fair value based on inputs that are not observable in the market. Consideration received from the sale of the SPECT business on January 1, 2026 was initially measured at fair value. See Note 8, “SPECT Business” for more information about the sale of the SPECT business in the first quarter of 2026.

Nonqualified Deferred Compensation Plan

The Company maintains the Lantheus Nonqualified Deferred Compensation Plan (the “LDCP”) for the benefit of certain key, highly-compensated employees and non-employee directors. The assets of the LDCP are invested in corporate-owned life insurance (“COLI”) and mutual funds at June 30, 2026. The mutual funds are classified as Level 1 of the fair value hierarchy because they are valued using quoted market prices. The liabilities of the LDCP are presented in other long-term liabilities in the Company’s condensed consolidated balance sheets. See Note 16, “Benefit Plans” for more information on the LDCP.

Perspective Therapeutics Inc. Equity Securities

At June 30, 2026, the Company held 11,677,339 shares of Perspective common stock (“Perspective Shares”). The Company accounts for its investment in Perspective Shares as an equity investment with a readily determinable fair value, as the securities are publicly traded on the New York Stock Exchange (“NYSE”). The fair value of the Perspective Shares is based on their closing price on the NYSE at the end of the fiscal period and is classified within Level 1 of the fair value hierarchy because the equity securities are valued using quoted market prices. The

fair value of the Perspective Shares as of June 30, 2026 was approximately $39.8 million based on a closing market price of $3.41 per share on June 30, 2026. The fair value of the Perspective Shares as of December 31, 2025 was approximately $32.1 million based on a closing market price of $2.75 per share on December 31, 2025. See Note 17, “Acquisitions” for further discussion of the Perspective transaction.

Radiopharm Theranostics Limited Equity Securities

The Company held 537,958,513 shares of Radiopharm common stock (“Radiopharm Shares”) as of June 30, 2026. The Company accounts for its investment in Radiopharm Shares as an equity investment with a readily determinable fair value, as the securities are publicly traded on the Australian Stock Exchange (“ASX”). The fair value of the Radiopharm Shares is based on their closing price on the ASX at the end of the fiscal period and is classified within Level 1 of the fair value hierarchy because the equity securities are valued using quoted market prices. The fair value of the Radiopharm Shares as of June 30, 2026 was approximately $7.0 million based on the converted closing market price of approximately $0.01 per share on June 30, 2026. The fair value of the Radiopharm Shares as of December 31, 2025 was approximately $9.0 million based on the converted closing market price of approximately $0.02 per share on December 31, 2025.

See Note 17, “Acquisitions” for further discussion of the Radiopharm transaction.

Contingent Consideration Liabilities

Evergreen Theragnostics, Inc.

Pursuant to the terms of the Agreement and Plan of Merger (the “Evergreen Merger Agreement”) with Evergreen and Shareholder Representative Services LLC governing the Company's acquisition of Evergreen in April 2025 (see Note 17, “Acquisitions”), the Company is required to pay up to $727.5 million in cash upon the achievement of specified milestones in connection with the development and commercialization of certain milestone products, as defined in the Evergreen Merger Agreement, and Octevy (also referred to as LNTH-2501), a registrational-stage positron emission tomography (“PET”) diagnostic imaging agent targeting neuroendocrine tumors. The Company records these possible payments as contingent consideration liabilities that are classified within Level 3 of the fair value hierarchy. The Company estimated the fair value of the contingent consideration liabilities associated with the sales milestones using a Monte Carlo simulation in a risk-neutral framework, whereby the achievement of the future revenue associated with the sales milestones was simulated using a geometric Brownian motion model. The Company estimated the fair value of the contingent consideration liability associated with the development and commercialization milestones using a probability-weighted discounted cash flow (“DCF”) approach. The most significant unobservable inputs with respect to these milestone products and Octevy, are the revenue volatility and probabilities of achieving regulatory milestones, respectively. A significant change in probability of payment of the first regulatory milestone payment for Octevy could result in a material fluctuation in the value of the contingent consideration liability.

Lantheus Biosciences Ltd.

Pursuant to the terms of the Sale and Purchase Agreement (the “LMI Purchase Agreement”) with Life Medical Group Limited (“Life Medical”) in connection with the Company’s acquisition of Lantheus Biosciences in July 2025 (see Note 17, “Acquisitions”), the Company is required to make certain earn-out and milestone payments as a percentage of and upon achievement of specified net sales thresholds, respectively, of Neuraceq and certain other imaging agents in Lantheus Bioscience’s pipeline. These contingent cash earn-out and milestone payments total up to $400.0 million.

In addition to the net sales earn-out and milestone payments, the Company also assumed a contingent consideration liability owed to Piramal Holdings SA (“Piramal”), pursuant to an assumed contract (the “Piramal SPA”). The Company is required to make cash payments of up to $30.0 million upon the achievement of specified earnings metrics of Lantheus Biosciences, as defined in the Piramal SPA.

The Company estimated the fair value of the contingent consideration liabilities using a Monte Carlo simulation model in a risk-neutral framework, whereby the achievement of the future revenue and other specified earnings metrics associated with the contingent payments were simulated using a geometric Brownian motion model. The most significant unobservable inputs with respect to Neuraceq and other imaging agents in Lantheus Biosciences’s pipeline include revenue volatility and the probability of commercial success. A significant change in the revenue volatility or forecasted commercial revenue could result in a material fluctuation in the value of the contingent consideration liability.

Significant changes in any of the probabilities of success, the probabilities as to the periods in which sales targets and milestones will be achieved, discount rates or underlying revenue forecasts would result in a higher or lower fair value measurement. For example, on June 26, 2026, the Company announced that the Food and Drug Association (the “FDA”) issued a Complete Response Letter (“CRL”) regarding the New Drug Application (“NDA”) for LNTH-2501, stating that the FDA could not approve the NDA by the June 29, 2026 extended Prescription Drug User Fee Act target action date due to unresolved third-party facility manufacturing-related conditions. The Company included this information in its assessment of the probability of success attached to the contingent consideration for LNTH-2501 as of June 30, 2026. As a result of the assessment of all such changes, including settlements, the Company determined the value of the contingent consideration liabilities related to the acquisitions to be $65.0 million at June 30, 2026, $29.3 million less than the December 31, 2025 value of $94.3 million, net of settlements. The Company records the contingent consideration liabilities at fair value with changes in estimated fair values recorded within operating expenses in the condensed consolidated statements of operations. The Company can give no assurance that the actual amounts paid, if any, in connection with the contingent consideration liabilities, will be consistent with any recurring fair value estimate of such contingent consideration liabilities.

Consideration Received From the Sale of the SPECT Business

On January 1, 2026, as a result of the sale of the Company’s SPECT business pursuant to the Equity and Asset Purchase Agreement, by and among Lantheus Medical, Lantheus MI Canada, Inc., Lantheus EU Limited, and Illuminated, SHINE SPECT, LLC, SHINE SPECT Medical Products, Ltd., and SHINE SPECT Limited (collectively referred to as “SHINE SPECT”), dated as of May 1, 2025 (the “SHINE SPECT Agreement”), the Company received consideration consisting of cash, notes receivable that may be settled in equity of Illuminated or in

cash depending on their specific terms, a right to receive additional cash on the earlier of January 1, 2030 or upon the occurrence of certain specified events, and the right to certain contingent consideration, as described below.

Installment Note

The Company received a promissory note from Illuminated, with a principal amount of $70.0 million that bears no interest and has a maturity date of June 14, 2028 (the “Installment Note”). The Company estimated the fair value of the Installment Note issued on January 1, 2026 using a probability-weighted discounted cash flow model. The discount upon issuance of the Installment Note is being recognized into other income, net in the Company’s condensed consolidated statements of operations for the periods in which the instrument remains outstanding.

Illuminated completed a qualified financing in February 2026, resulting in the conversion of the Installment Note into Series E-1 convertible preferred stock of Illuminated (the “Series E-1 Preferred”) on April 6, 2026 (the “Conversion Date”). On the Conversion Date and in accordance with the Installment Note, the Company entered into an Adoption Agreement with Illuminated pursuant to which the Company acquired 2,545,454 shares of Series E-1 Preferred upon the conversion in full and cancellation of the $70.0 million Installment Note at a conversion price of $27.50 per share. The Company estimated the fair value of the Series E-1 Preferred at $70.0 million based on the contemporaneous price paid by third-party investors for identical Series E-1 Preferred shares in Illuminated’s February 2026 qualified financing and in subsequent financings during the three months ended June 30, 2026. At the Conversion Date, the carrying value of the Installment Note was $70.0 million, with an unamortized discount of $2.5 million, and the fair value of the Series E-1 Preferred was $70.0 million, resulting in a $2.5 million gain on conversion of the Installment Note. The gain on conversion of the Installment Note is included in other income, net on the Company’s condensed consolidated statements of operations for the three and six months ended June 30, 2026.

The Series E-1 Preferred is convertible, at any time upon the election of the holder, into shares of Illuminated common stock on a one-for-one-basis, votes on an as-converted basis alongside other shares of Illuminated’s preferred stock, and entitles the holders of the Series E-1 Preferred, voting as a single class along with the holders of all other shares of Series E convertible preferred stock, to elect one member to Illuminated’s board of directors, subject to certain minimum ownership thresholds. The Series E-1 Preferred are equity securities and within the scope of ASC 321, “Investments - Equity Securities.” The Company elected the measurement alternative for this investment in the Series E-1 Preferred because the shares do not have a readily determinable fair value and therefore are excluded from the assets and liabilities measured at fair value on a recurring basis table above. Under this alternative, the Company measures investments without readily determinable fair values at cost, less impairment, adjusted for changes from observable price changes in orderly transactions for identical or similar investments. As of June 30, 2026, the carrying value of the investment in Series E-1 Preferred was $70.0 million and is included in investment in equity securities on the Company’s condensed consolidated balance sheet.

Seller Note

The Company received an unsecured promissory note from SHINE SPECT (the “Seller Note”), with a principal amount of $20.0 million, an 8.0% annual interest rate payable semi-annually of which up to half can be paid in-kind, and a maturity date of the earlier of January 1, 2029 or completion of an initial public offering by Illuminated (“SHINE IPO”). The terms of the Seller Note are governed by a Subordination Agreement dated January 1, 2026, by and between Lantheus Medical, SHINE SPECT and other parties (the “Subordination Agreement”). Pursuant to the Seller Note, if a change in control or a material financing (each as defined in the Seller Note) occurs on or prior to the maturity date, the Company has the option to require a cash repayment equal to the outstanding principal amount of the Seller Note plus accrued interest, subject to the terms of the Subordination Agreement. In addition, SHINE SPECT has the option to prepay the Seller Note prior to the maturity date, subject to the Subordination Agreement. At issuance, the Company concluded that certain contingent repayment and acceleration features embedded within the Seller Note require separate accounting as an embedded derivative under ASC 815, “Derivatives and Hedging.” Accordingly, the Company recognized an immaterial derivative asset related to those features. The Company estimated the fair value of the Seller Note on January 1, 2026 using a discounted cash flow technique that incorporated probability-weighted repayment scenarios including scenarios involving the timing of payments. In connection with that analysis, the Company identified an immaterial embedded derivative that was bifurcated from the host debt contract. The carrying amount of the host debt instrument was determined after giving effect to the bifurcation of the embedded derivative. The resulting debt discount on the host debt-instrument is being accreted into other income, net in the Company’s condensed consolidated statements of operations over the period the Seller Note remains outstanding.

Deferred Cash Purchase Price

The Company will receive $20.0 million in cash on the earlier of (i) January 1, 2029 or (ii) a SHINE IPO (“Deferred Cash Purchase Price”). If the Deferred Cash Purchase Price is not paid by January 1, 2029, the Company will be entitled to an additional $5.0 million of cash

consideration, for a total of $25.0 million in cash to be paid no later than January 1, 2030. The Company estimated the fair value of the Deferred Cash Purchase Price on January 1, 2026 using a probability-weighted discounted cash flow technique that incorporated various repayment timing scenarios, including the potential timing of a SHINE IPO. In connection with its accounting analysis of the Deferred Cash Purchase Price, the Company identified an immaterial derivative related to certain contingent repayment features and bifurcated those features from the host contract. The resulting discount on the host contract is being accreted into other income, net in the Company’s condensed consolidated statements of operations over the period in which the instrument remains outstanding.

Net Contingent Consideration

The Company may earn up to $30.0 million in a combination of cash and capital stock of Illuminated upon exceeding specified annual and cumulative revenue milestones of the SPECT business for each calendar year through December 31, 2027 (“Contingent Consideration Receivable”). The Company estimated the fair value of the Contingent Consideration Receivable on January 1, 2026 associated with the revenue annual and cumulative milestones using a Monte Carlo simulation in a risk-neutral framework, whereby the achievement of the future revenue associated with the sales milestones was simulated using a geometric Brownian motion model. The Company estimated the fair value of the Contingent Consideration Receivable to be $6.5 million on January 1, 2026.

A contingent consideration payable of $1.4 million for the 2025 fiscal year was payable by the Company pursuant to terms of the SHINE SPECT Agreement, and settled shortly after January 1, 2026, and was included in the computation of the net consideration received.

All components of net consideration received were measured at fair value on January 1, 2026 in computing the gain on sale of business. The fair value of total net consideration received by the Company on January 1, 2026 was approximately $131.2 million, including $32.1 million in cash, as well as other instruments as follows: