Y-mAbs Therapeutics, Inc.

The Company recognized royalty revenue from distribution partners of $3,818,000 and $3,218,000 in the six months ended June 30, 2025 and 2024, respectively.Product sales to certain distribution partners that accounted for more than 10% of net product revenue for the three and six months ended June 30, 2025 and 2024 consists of the following: Three months ended June 30, Six months ended June 30, 2025 2024 2025 2024 McKesson 38% 38% 34% 43%Cardinal Health 27 18 22 19 INPHARMUS 10 — 15 — Cencora 11 11 13 17 SciClone 9 15 8 8 Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson 30 % 51 %

McKesson, Cardinal Health and Cencora accounted for 41%, 20% and 16%, respectively of the Company’s net product revenue for the year ended December 31, 2024.

The Company recognized royalty revenue from distribution partners of $4,351,000 and $3,814,000 in the nine months ended September 30, 2024 and 2023, respectively.Product sales to certain distribution partners that accounted for more than 10% of total product revenue, net, for the three and nine months ended September 30, 2024 and 2023 consists of the following: Three months ended September 30, Nine months ended September 30, 2024 2023 2024 2023 McKesson 48% 48% 45% 45%Cardinal Health 21 14 20 13 Cencora 15 18 17 22 WEP — 15 3 9 As of September 30, 2024, the Company had recorded on the Consolidated Balance Sheets accounts receivable of approximately $19,916,000, of which $2,816,000 represents an unbilled portion to which the Company has unconditional rights to collect the consideration related to product sales to the Company’s distributor in Western Europe, WEP.Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson, Cencora, WEP and Cardinal Health accounted for 46%, 22%, 10% and 13%, respectively, of the Company’s net product revenue for the year ended December 31, 2023.

McKesson 38 % 46 % 43 % 44 %

McKesson, AmerisourceBergen, Cardinal Health and WEP accounted for 45%, 29%, 13% and 12%, respectively, of the Company’s product revenue, net for the three months ended March 31, 2023.

McKesson, AmerisourceBergen, and Cardinal Health accounted for 71%, 17%, and 10%, respectively, of the Company’s product revenue, net for the year ended December 31, 2022.

McKesson and AmerisourceBergen accounted for 78% and 14%, respectively, of the Company’s product revenue, net, for the three months ended September 30, 2022.

McKesson, AmerisourceBergen and Cardinal Health accounted for 71%, 10% and 11%, respectively, of the Company’s product revenue, net, for the three months ended June 30, 2022.

McKesson, AmerisourceBergen, and Cardinal Health accounted for 60%, 25%, and 11%, respectively, of our gross product revenue for the three months ended March 31, 2022.

McKesson and AmerisourceBergen accounted for 73.2% and 17.6%, respectively, of our gross product revenue for the year ended December 31, 2021.

McKesson and AmerisourceBergen accounted for 66% and 24%, respectively, of the Company’s gross product revenue for the three months ended September 30, 2021.

Mckesson and AmerisourceBergen accounted for 75% and 19%, respectively, of the Company’s gross product revenue for the three months ended June 30, 2021.

Mckesson and Cardinal Health accounted for 80% and 16%, respectively, of our gross product revenue for the three months ended March 31, 2021.

The Company recognized royalty revenue from distribution partners of $3,818,000 and $3,218,000 in the six months ended June 30, 2025 and 2024, respectively.Product sales to certain distribution partners that accounted for more than 10% of net product revenue for the three and six months ended June 30, 2025 and 2024 consists of the following: Three months ended June 30, Six months ended June 30, 2025 2024 2025 2024 McKesson 38% 38% 34% 43%Cardinal Health 27 18 22 19 INPHARMUS 10 — 15 — Cencora 11 11 13 17 SciClone 9 15 8 8 Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson, Cardinal Health and Cencora accounted for 41%, 20% and 16%, respectively of the Company’s net product revenue for the year ended December 31, 2024.

The Company recognized royalty revenue from distribution partners of $4,351,000 and $3,814,000 in the nine months ended September 30, 2024 and 2023, respectively.Product sales to certain distribution partners that accounted for more than 10% of total product revenue, net, for the three and nine months ended September 30, 2024 and 2023 consists of the following: Three months ended September 30, Nine months ended September 30, 2024 2023 2024 2023 McKesson 48% 48% 45% 45%Cardinal Health 21 14 20 13 Cencora 15 18 17 22 WEP — 15 3 9 As of September 30, 2024, the Company had recorded on the Consolidated Balance Sheets accounts receivable of approximately $19,916,000, of which $2,816,000 represents an unbilled portion to which the Company has unconditional rights to collect the consideration related to product sales to the Company’s distributor in Western Europe, WEP.Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson, AmerisourceBergen and Cardinal Health, accounted for 51%, 25%, and 22%, respectively, of the Company’s product revenue, net for the three months ended March 31, 2024.

McKesson, Cencora, WEP and Cardinal Health accounted for 46%, 22%, 10% and 13%, respectively, of the Company’s net product revenue for the year ended December 31, 2023.

McKesson, SciClone, AmerisourceBergen and Cardinal Health accounted for 46%, 20%, 18% and 12% respectively, of the Company’s product revenue, net, for the three months ended June 30, 2023.

McKesson, AmerisourceBergen, Cardinal Health and WEP accounted for 45%, 29%, 13% and 12%, respectively, of the Company’s product revenue, net for the three months ended March 31, 2023.

McKesson, AmerisourceBergen, WEP and Cardinal Health accounted for 46%, 22%, 10% and 13%, respectively, of the Company’s product revenue, net for the year ended December 31, 2023.

McKesson, AmerisourceBergen and Cardinal Health accounted for 71%, 10% and 11%, respectively, of the Company’s product revenue, net, for the three months ended June 30, 2022.

McKesson, AmerisourceBergen, and Cardinal Health accounted for 60%, 25%, and 11%, respectively, of our gross product revenue for the three months ended March 31, 2022.

Mckesson and Cardinal Health accounted for 75% and 19%, respectively, of our gross product revenue for the three months ended June 30, 2021.

Mckesson and Cardinal Health accounted for 80% and 16%, respectively, of our gross product revenue for the three months ended March 31, 2021.

The Company recognized royalty revenue from distribution partners of $3,818,000 and $3,218,000 in the six months ended June 30, 2025 and 2024, respectively.Product sales to certain distribution partners that accounted for more than 10% of net product revenue for the three and six months ended June 30, 2025 and 2024 consists of the following: Three months ended June 30, Six months ended June 30, 2025 2024 2025 2024 McKesson 38% 38% 34% 43%Cardinal Health 27 18 22 19 INPHARMUS 10 — 15 — Cencora 11 11 13 17 SciClone 9 15 8 8 Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson, Cardinal Health and Cencora accounted for 41%, 20% and 16%, respectively of the Company’s net product revenue for the year ended December 31, 2024.

The Company recognized royalty revenue from distribution partners of $4,351,000 and $3,814,000 in the nine months ended September 30, 2024 and 2023, respectively.Product sales to certain distribution partners that accounted for more than 10% of total product revenue, net, for the three and nine months ended September 30, 2024 and 2023 consists of the following: Three months ended September 30, Nine months ended September 30, 2024 2023 2024 2023 McKesson 48% 48% 45% 45%Cardinal Health 21 14 20 13 Cencora 15 18 17 22 WEP — 15 3 9 As of September 30, 2024, the Company had recorded on the Consolidated Balance Sheets accounts receivable of approximately $19,916,000, of which $2,816,000 represents an unbilled portion to which the Company has unconditional rights to collect the consideration related to product sales to the Company’s distributor in Western Europe, WEP.Revenue from product sales is recorded as net of applicable provisions for rebates, chargebacks, discounts, distribution-related fees and other sales-related deductions.

McKesson, Cencora, WEP and Cardinal Health accounted for 46%, 22%, 10% and 13%, respectively, of the Company’s net product revenue for the year ended December 31, 2023.

McKesson, SciClone, AmerisourceBergen and Cardinal Health accounted for 46%, 20%, 18% and 12% respectively, of the Company’s product revenue, net, for the three months ended June 30, 2023.

McKesson, AmerisourceBergen, Cardinal Health, and WEP accounted for 45%, 29%, 13%, and 12%, respectively, of our gross product revenue for the three months ended March 31, 2023.

McKesson, AmerisourceBergen, and Cardinal Health accounted for 70.8%, 17.4%, and 10.1%, respectively, of our gross product revenue for the year ended December 31, 2022.

McKesson and AmerisourceBergen accounted for 78% and 14%, respectively, of the Company’s gross product revenue for the three months ended September 30, 2022.

McKesson, AmerisourceBergen and Cardinal Health accounted for 71%, 10% and 11%, respectively, of the Company’s product revenue, net, for the three months ended June 30, 2022.

McKesson, AmerisourceBergen, and Cardinal Health accounted for 60%, 25%, and 11%, respectively, of our gross product revenue for the three months ended March 31, 2022.

McKesson and AmerisourceBergen accounted for 73.2% and 17.6%, respectively, of our gross product revenue for the year ended December 31, 2021.

McKesson and AmerisourceBergen accounted for 66% and 24%, respectively, of the Company’s gross product revenue for the three months ended September 30, 2021.