Monalizumab

MARSEILLE, France--(BUSINESS WIRE)--Regulatory News: Innate Pharma SA (Euronext Paris: IPH; Nasdaq: IPHA) (“Innate” or the “Company”) today reported its consolidated financial results for the six months ended June 30, 2025. The consolidated financial statements are attached to this press release. “With key milestones anticipated over the next 12 months, our primary focus will be on progressing what we believe are our most promising and highest-value clinical assets and advancing our next ADCs toward development. In line with this strategic focus and in a challenging funding environment, we are taking necessary action to focus our resources on what we believe are the programs with the highest potential to deliver value for both patients and shareholders, and we therefore plan to streamline the size of the organization,” said Jonathan Dickinson, Chief Executive Officer of Innate Pharma. “We made meaningful progress during the first half of the year in our pipeline and are determined to build on this momentum. At ASCO, we presented a Trial In Progress for our Nectin-4 ADC, IPH4502, which is progressing rapidly through Phase 1 enrollment; and we shared long-term follow-up data for lacutamab, for which preparation of the confirmatory Phase 3 trial protocol is close to completion, following discussions with the FDA and EMA. Looking ahead, we have a number of important catalysts, including first patient data for IPH4502 in H1 2026, and high level read-out of AstraZeneca’s PACIFIC-9 Phase 3 trial with monalizumab in H2 2026.” 1 Including short term investments (€6.3 million) and non-current financial instruments (€10.4 million) Webcast and conference call will be held today at 2:00 p.m. CEST (8:00 a.m. ET) Access to live webcast: https://events.q4inc.com/attendee/642492835 Participants may also join via telephone using the registration link below: https://registrations.events/direct/Q4I970472 This information can also be found on the Investors section of the Innate Pharma website, www.innate-pharma.com. A replay of the webcast will be available on the Company website for 90 days following the event. Pipeline highlights: Strategic focus Innate Pharma plans to prioritize its investment on what it believes are its highest-value clinical assets, IPH4502, lacutamab, and monalizumab (partnered with AstraZeneca); its preclinical research and development (R&D) efforts will focus on advancing the next Antibody Drug Conjugates (ADCs) toward development, leveraging its pipeline of innovative targets. IPH4502 (Nectin-4 ADC, proprietary): IPH4502 is Innate’s novel and differentiated topoisomerase I inhibitor ADC targeting Nectin-4. The first patient was dosed in a Phase 1 study in January 2025. The Phase 1 study will assess the safety, tolerability, and preliminary efficacy of IPH4502 in advanced solid tumors known to express Nectin-4, including but not limited to urothelial carcinoma, non-small cell lung, breast, ovarian, gastric, esophageal, and colorectal cancers. The study plans to enroll approximately 105 patients. A Trial in Progress Poster was shared at the ASCO Annual Meeting in June 2025. Enrollment is in progress and expected to be completed at the end of 2025 or in the first quarter of 2026. New preclinical data were presented at the American Association for Cancer Research (AACR) Annual Meeting 2025. IPH4502 demonstrated superior preclinical anti-tumor activity compared to enfortumab vedotin (EV) in urothelial carcinoma (UC) models with low or heterogeneous Nectin-4 expression, as well as in models resistant to EV. Beyond UC, IPH4502 also exhibited anti-tumor activity in preclinical models of triple-negative breast cancer, head and neck squamous cell carcinoma, and esophageal cancer, suggesting broader potential clinical applicability. Lacutamab (anti-KIR3DL2 antibody, proprietary): Cutaneous T Cell Lymphoma In February 2025, the FDA granted Breakthrough Therapy Designation to lacutamab for relapsed or refractory Sézary syndrome (SS) based on TELLOMAK Phase 2 results demonstrating efficacy and a favorable safety profile in patients with advanced SS, heavily pretreated, post-mogamulizumab. Breakthrough Therapy Designation is intended to accelerate the development and regulatory review in the U.S. of drugs that are intended to treat a serious condition. At the 2025 ASCO Annual Meeting, updated long-term data from the Phase 2 TELLOMAK trial reinforced the clinical activity and durability of lacutamab in relapsed/refractory SS and mycosis fungoides (MF). In SS, lacutamab achieved a 42.9% ORR with a median duration of response of 25.6 months, while in MF, responses were observed regardless of KIR3DL2 expression, with a median PFS of 10.2 months. Across both cohorts, lacutamab was well tolerated, with no safety concerns and sustained improvements in quality of life. Preparation of the confirmatory Phase 3 trial protocol is close to completion, following discussions with the FDA and EMA. Innate is evaluating potential paths forward to advance lacutamab toward Phase 3 initiation, including discussions with partners and investors. Peripheral T Cell lymphoma (PTCL) The Phase 2 KILT (anti-KIR in T Cell Lymphoma) trial, an investigator-sponsored, randomized controlled trial, led by the Lymphoma Study Association, to evaluate lacutamab in combination with GEMOX (gemcitabine and oxaliplatin) chemotherapy versus GEMOX alone, in patients with KIR3DL2-expressing relapsed/refractory PTCL, is ongoing and continues to recruit patients. Monalizumab (anti-NKG2A antibody), partnered with AstraZeneca: The Phase 3 PACIFIC-9 trial run by AstraZeneca evaluating durvalumab (anti-PD‑L1) in combination with monalizumab or AstraZeneca’s oleclumab (anti-CD73) in patients with unresectable, Stage III non-small cell lung cancer (NSCLC) who have not progressed following definitive platinum-based concurrent chemoradiation therapy (CRT) is ongoing. Enrollment in the trial is completed, and high level read-out is expected in H2 2026. At the ASCO Annual Meeting in June 2025, AstraZeneca presented updated results from the Phase 2 NeoCOAST-2 trial evaluating neoadjuvant and adjuvant durvalumab-based combinations in resectable NSCLC. The regimen including durvalumab, monalizumab, and chemotherapy (Arm 2, n=70) showed 25.7% pathological complete response (pCR) and 50.0% major pathologic response (mPR). ANKET® (Antibody-based NK cell Engager Therapeutics): ANKET® is Innate’s proprietary platform for developing next-generation, multi-specific NK cell engagers to treat certain types of cancer. IPH6501 (ANKET® anti-CD20 with IL-2V, proprietary) The Phase 1/2 clinical trial is evaluating IPH6501 in B-cell Non-Hodgkin’s lymphoma (B-NHL). The study is planned to enroll up to 184 patients. Clinical sites are open in the US, Australia, and France. The dose escalation phase in the trial has been completed. Limited signals of activity were observed during the escalation phase, and maximum tolerated dose (MTD) is currently being explored to further assess clinical relevance. Clinical data are expected in late 2025 or beginning of 2026. IPH6101 (ANKET® anti-CD123, proprietary) Innate regained the rights to SAR’579/IPH6101 in July 2025. The Company is in the process of receiving the product data from Sanofi relating to the Sanofi-led Phase 1/2 study and Phase 2 preliminary dose expansion of the trial. SAR’514/IPH6401 (BCMA ANKET®, Sanofi) As previously disclosed, Sanofi has opted to pursue the development of SAR’514/IPH6401 (BCMA ANKET ® ) in autoimmune indications under the terms of the 2016 License Agreement. The Sanofi-led Phase 1/2 study (clinical study identifier: NCT05839626) for the treatment of patients with relapsed or refractory multiple myeloma has been terminated early, in line with the decision to focus SAR’514/IPH6401 development in autoimmune indications. Preclinical ANKET IPH62 (partnered with Sanofi): IPH62 is an NK-cell engager program targeting B7-H3 from Innate’s ANKET ® platform, which is under preclinical development. Following a research collaboration period and upon candidate selection, Sanofi will be responsible for all development, manufacturing and commercialization. Sanofi still retains an option on one additional ANKET ® target under the terms of the 2022 research collaboration and license agreement. Other assets IPH5201 (anti-CD39), partnered with AstraZeneca : The MATISSE Phase 2 clinical trial conducted by Innate in neoadjuvant lung cancer for IPH5201, an anti-CD39 blocking monoclonal antibody developed in collaboration with AstraZeneca, is ongoing, and recruitment is on track. IPH5301 (anti-CD73): The investigator-sponsored CHANCES Phase 1 trial of IPH5301 with Institut Paoli-Calmettes is ongoing. Corporate Update: Innate Pharma plans to prioritize its investment on what it believes are its highest-value clinical assets, IPH4502, lacutamab, and monalizumab (partnered with AstraZeneca); its preclinical research and development (R&D) efforts will focus on advancing the next ADCs toward development, leveraging its pipeline of innovative targets. In line with such strategic focus and its objectives, the Company intends to streamline its organization. Staffing levels are expected to decrease overall by about 30% total, including through attrition. The planned layoffs will be implemented through a redundancy plan that is subject to consultation with the Workers’ Council and endorsement by the French authorities (Dreets). The implementation of the change is expected to be completed during the first half of 2026. Eric Vivier, CSO, has decided to return to academic research full time, effective January 1, 2026, and he will continue to support the Company’s innovation as an advisor to the R&D Committee of the Board of Directors. Innate will continue accessing innovation through academic collaborations, including Eric Vivier’s lab at the Center for Immunology of Marseille-Luminy (CIML). As Chief Operating Officer (COO), Yannis Morel, will continue to be responsible for preclinical research and development, and effective January 1, 2026 will assume CSO responsibilities. As announced on April 23, 2025, Sanofi and Innate agreed to terminate the 2016 Research Collaboration and Licence Agreement (the “2016 Agreement”) as it relates to SAR’579/IPH6101 (CD123 ANKET ® ). As part of their discussions with regards to the review of the 2016 Agreement, Sanofi and Innate announced the investment by Sanofi of up to €15 million in new shares of Innate. Sanofi then subscribed to 8,345,387 new ordinary shares of Innate, at a price of €1.7974 per share, representing a total capital increase of €14,999,998.59 (€417,269.35 in nominal amount and €14,582,729.24 of issue premium) representing 9.05% of Innate’s total outstanding shares as of the time of such capital increase. On May 22, 2025, after approval at the Annual General Meeting, Innate Pharma changed its corporate governance from an executive board/supervisory board structure to a CEO/board of directors with Irina Staatz-Granzer as Chairwoman and Jonathan Dickinson as Chief Executive Officer. This transformation is part of the Company’s strategic plan to simplify and align its governance with international standards. As part of the change, two seasoned biotech executives, Marty J. Duvall and Christian Itin, joined the Board of Directors. In addition, a new R&D Committee has been established as a committee of the Board of Directors, the role of which is to analyze research and development opportunities for the Company's products. Its members are Bpifrance Participations, represented by Olivier Martinez, also appointed Chairman of the Research and Development Committee, Véronique Chabernaud and Christian Itin. As of June 30, 2025, the balance available under our April 2023 sales agreement under the At-The-Market program remains at $75 million. Stéphanie Cornen was appointed Vice President, Investor Relations, Communications and Commercial Strategy after Henry Wheeler, VP Investor Relations and Communications resigned from his position in order to pursue another opportunity outside the Company. Stéphanie Cornen joined Innate in 2012. Between 2012 and 2022, she held several R&D positions, contributing to the advancement of programs across various development stages. Starting in 2022, she took on responsibilities in corporate development and portfolio strategy, while supporting investor relations. Stéphanie Cornen holds a PharmD and a PhD from Aix-Marseille University, as well as an Executive MBA from HEC Paris. Financials highlights for the first half of 2025: The key elements of Innate’s financial position and financial results as of and for the six-month period ended June 30, 2025 are as follows: Cash, cash equivalents, short-term investments and financial assets amounting to €70.4 million (€m) as of June 30, 2025 (€91.1m as of December 31, 2024). As of June 30, 2025, financial liabilities amount to €27.0m (€31.0m as of December 31, 2024). This change is mainly due to loan repayments. Revenue and other income amounted to €4.9m in the first half of 2025 (€12.3m in the first half of 2024) and mainly comprised of: Revenue from collaboration and licensing agreements, which mainly resulted from the partial or entire recognition of the proceeds received pursuant to the agreements with AstraZeneca and Sanofi. They are recognized when the entity's performance obligation is met. They are recognized at a point in time or spread over time according to the percentage of completion of the work that the Company is committed to carry out under these agreements: (i) Revenue from collaboration and licensing agreements for monalizumab decreased by €2.9m to €0.1m in the first half of 2025 (€3.0m in the first half of 2024). This change is mainly due to the progress of Phase 1/2 trials close to termination. (ii) Revenue related to the license and collaboration agreement signed with Sanofi in 2016 decreased by €4.0m. These revenues are nil for the first half of 2025 as compared to €4.0m for the first half of 2024. On April 15, 2024, the Company announced the treatment of the first patient in the Phase 2 dose expansion part of the Sanofi-sponsored clinical trial evaluating NK Cell Engager SAR443579/ IPH6101 in various blood cancers. Under the terms of the 2016 agreement, this trial progress triggered a milestone payment of €4.0 million fully recognized in revenue during the first quarter of 2024. This amount was received by the Company on May 17, 2024. (iii) Revenue related to the research collaboration and licensing agreement signed with Sanofi in 2022 remained constant over the period, with revenue amounting to €0.2 million for the first half of 2025, as for the first half of 2024. As previously disclosed, on January 25, 2023, the Company announced the expiration of the waiting period under the Hart-Scott-Rodino (HSR) Antitrust Improvements Act of 1976 and the effectiveness of the licensing agreement as of January 24, 2023. Consequently, the Company received an upfront payment of €25.0 million in March 2023, including €18.5 million for the exclusive license, €1.5 million for the research activities and €5.0 million for the option on two additional targets. The €18.5 million upfront payment relating to the exclusive license was fully recognized in revenue as of June 30, 2023. The research work upfront payment is recognized on a straight-line basis over the duration of the research activities that the Company has agreed to carry out. On December 19, 2023, the Company announced that Sanofi had exercised one of the two license options for a new program based on the Company's ANKET ® platform. This decision triggered a milestone payment of €15.0m, including €13.3m for the exclusive license, fully recognized in revenue as of December 31, 2023, and €1.7m for research work to be carried out by the Company as well as the recognition in revenue of an amount of €2.5m initially received in March 2023 in connection with this option. On October 9, 2024, the Company received a termination letter for the license agreement concerning this option. The termination ends the research work. The revenue of €1.7 million was therefore fully recognized as revenue on December 31, 2024. Revenue from research work on the first license amounted to €0.2 million for the first half of 2025. Amounts not recognized in revenue are classified as deferred revenue. Government funding for research expenditures of €3.2m in the first half of 2025 (€4.1m in the first half of 2024), decreasing by €0.9 million, or 21.3% in connection with decrease in eligible subcontracting expenses following progress in studies and research programs. Revenue from collaboration and licensing agreements, which mainly resulted from the partial or entire recognition of the proceeds received pursuant to the agreements with AstraZeneca and Sanofi. They are recognized when the entity's performance obligation is met. They are recognized at a point in time or spread over time according to the percentage of completion of the work that the Company is committed to carry out under these agreements: (i) Revenue from collaboration and licensing agreements for monalizumab decreased by €2.9m to €0.1m in the first half of 2025 (€3.0m in the first half of 2024). This change is mainly due to the progress of Phase 1/2 trials close to termination. (ii) Revenue related to the license and collaboration agreement signed with Sanofi in 2016 decreased by €4.0m. These revenues are nil for the first half of 2025 as compared to €4.0m for the first half of 2024. On April 15, 2024, the Company announced the treatment of the first patient in the Phase 2 dose expansion part of the Sanofi-sponsored clinical trial evaluating NK Cell Engager SAR443579/ IPH6101 in various blood cancers. Under the terms of the 2016 agreement, this trial progress triggered a milestone payment of €4.0 million fully recognized in revenue during the first quarter of 2024. This amount was received by the Company on May 17, 2024. (iii) Revenue related to the research collaboration and licensing agreement signed with Sanofi in 2022 remained constant over the period, with revenue amounting to €0.2 million for the first half of 2025, as for the first half of 2024. As previously disclosed, on January 25, 2023, the Company announced the expiration of the waiting period under the Hart-Scott-Rodino (HSR) Antitrust Improvements Act of 1976 and the effectiveness of the licensing agreement as of January 24, 2023. Consequently, the Company received an upfront payment of €25.0 million in March 2023, including €18.5 million for the exclusive license, €1.5 million for the research activities and €5.0 million for the option on two additional targets. The €18.5 million upfront payment relating to the exclusive license was fully recognized in revenue as of June 30, 2023. The research work upfront payment is recognized on a straight-line basis over the duration of the research activities that the Company has agreed to carry out. On December 19, 2023, the Company announced that Sanofi had exercised one of the two license options for a new program based on the Company's ANKET ® platform. This decision triggered a milestone payment of €15.0m, including €13.3m for the exclusive license, fully recognized in revenue as of December 31, 2023, and €1.7m for research work to be carried out by the Company as well as the recognition in revenue of an amount of €2.5m initially received in March 2023 in connection with this option. On October 9, 2024, the Company received a termination letter for the license agreement concerning this option. The termination ends the research work. The revenue of €1.7 million was therefore fully recognized as revenue on December 31, 2024. Revenue from research work on the first license amounted to €0.2 million for the first half of 2025. Amounts not recognized in revenue are classified as deferred revenue. Government funding for research expenditures of €3.2m in the first half of 2025 (€4.1m in the first half of 2024), decreasing by €0.9 million, or 21.3% in connection with decrease in eligible subcontracting expenses following progress in studies and research programs. Operating expenses are €30.3m in the first half of 2025 (€38.7m in the first half of 2024), of which 67.8% (€20.5m) are related to R&D. R&D expenses decreased by €8.6m to €20.5m in the first half of 2025 (€29.1m in the first half of 2024). This change is mainly explained by direct R&D expenses, which slightly decreased by €7.3 million or 43% to reach €9.7 million for the first half of 2025. This decrease is related to the phasing of studies (maturity of clinical studies on lacutamab, discontinuation of preclinical studies, and start of phase 1 of our antibody-drug conjugate (ADC) program). General and administrative (G&A) expenses increased by €0.2m to €9.8m in the first half of 2025 (€9.6m in the first half of 2024) mainly resulting from an increase in personnel expenses linked to provisions for risks and charges, bringing personnel expenses to €4.8 million in the first half of 2025, offset by a €0.5 million decrease in non-scientific and consulting fees, which amounts to €1.4 million in the first half of 2025, resulting mainly from greater use of recruitment agencies in 2024 (for the establishment of the clinical department), which was not renewed in 2025. R&D expenses decreased by €8.6m to €20.5m in the first half of 2025 (€29.1m in the first half of 2024). This change is mainly explained by direct R&D expenses, which slightly decreased by €7.3 million or 43% to reach €9.7 million for the first half of 2025. This decrease is related to the phasing of studies (maturity of clinical studies on lacutamab, discontinuation of preclinical studies, and start of phase 1 of our antibody-drug conjugate (ADC) program). General and administrative (G&A) expenses increased by €0.2m to €9.8m in the first half of 2025 (€9.6m in the first half of 2024) mainly resulting from an increase in personnel expenses linked to provisions for risks and charges, bringing personnel expenses to €4.8 million in the first half of 2025, offset by a €0.5 million decrease in non-scientific and consulting fees, which amounts to €1.4 million in the first half of 2025, resulting mainly from greater use of recruitment agencies in 2024 (for the establishment of the clinical department), which was not renewed in 2025. A net financial gain of €4.1m in the first half of 2025 (€1.5m in the first half of 2024). This change is mainly due to a favorable variation in net foreign exchange gain with its favorable impact on the collaboration liabilities recorded during the first half of 2025 in connection with the change in the dollar exchange rate despite an unfavorable variation in income resulting from financial assets and fair value revaluation due to an unfavorable effect of investment rates recorded on the financial markets. A net loss of €21.3m for the first half of 2025 (net income of €24.8m for the first half of 2024). The table below summarizes the IFRS consolidated financial statements as of and for the six months ended June 30, 2025, including 2024 comparative information. In thousands of euros, except for data per share June 30, 2025 June 30, 2024 Revenue and other income 4,860 12,345 Research and development expenses (20,520) (29,076) General and administrative expenses (9,767) (9,582) Operating expenses (30,287) (38,657) Operating income (loss) (25,427) (26,313) Net financial income (loss) 4,083 1,549 Income tax expense — — Net income (loss) (21,344) (24,764) Weighted average number of shares ( in thousands) : 86,937 80,872 - Basic income (loss) per share (0.25) (0.31) - Diluted income (loss) per share (0.25) (0.31) June 30, 2025 December 31, 2024 Cash, cash equivalents and financial assets 70,417 91,051 Total assets 92,937 111,059 Total shareholders’ equity 5,144 8,834 Total financial debt 27,029 30,995 About Innate Pharma: Innate Pharma S.A. is a global, clinical-stage biotechnology company developing immunotherapies for cancer patients. Leveraging its antibody-engineering expertise, the company has developed innovative therapeutic approaches, including Antibody Drug Conjugates (ADC), monoclonal antibodies (mAbs) and multi-specific NK Cell Engagers through its proprietary ANKET® (Antibody-based NK cell Engager Therapeutics) platform. Innate’s portfolio includes IPH4502, a differentiated Nectin-4 ADC in development in solid tumors, lacutamab, an anti-KIR3DL2 mAb developed in advanced forms of cutaneous T cell lymphomas and peripheral T cell lymphomas, and monalizumab, an anti-NKG2A antibody developed in collaboration with AstraZeneca in non-small cell lung cancer. Innate Pharma is a trusted partner to biopharmaceutical companies such as Sanofi and AstraZeneca, as well as renowned research institutions, working together to accelerate innovation, research and development for the benefit of patients. Headquartered in Marseille, France with a US office in Rockville, MD, Innate Pharma is listed on Euronext Paris and Nasdaq in the US. Learn more about Innate Pharma at www.innate-pharma.com. Follow us on LinkedIn and X. Information about Innate Pharma shares: ISIN code FR0010331421 Ticker code Euronext: IPH Nasdaq: IPHA LEI 9695002Y8420ZB8HJE29 Disclaimer on forward-looking information and risk factors: This press release contains certain forward-looking statements, including those within the meaning of applicable securities laws, including the Private Securities Litigation Reform Act of 1995. The use of certain words, including “anticipate,” “believe,” “can,” “could,” “estimate,” “expect,” “may,” “might,” “potential,” “expect” “should,” “will,” or the negative of these and similar expressions, is intended to identify forward-looking statements. Although the Company believes its expectations are based on reasonable assumptions, these forward-looking statements are subject to numerous risks and uncertainties, which could cause actual results to differ materially from those anticipated. These risks and uncertainties include, among other things, the uncertainties inherent in research and development, including related to safety, progression of and results from its ongoing and planned clinical trials and preclinical studies, review and approvals by regulatory authorities of its product candidates, the Company’s reliance on third parties to manufacture its product candidates, the Company’s commercialization efforts and the Company’s continued ability to raise capital to fund its development. For an additional discussion of risks and uncertainties, which could cause the Company's actual results, financial condition, performance or achievements to differ from those contained in the forward-looking statements, please refer to the Risk Factors (“Facteurs de Risque") section of the Universal Registration Document filed with the French Financial Markets Authority (“AMF”), which is available on the AMF website http://www.amf-france.org or on Innate Pharma’s website, and public filings and reports filed with the U.S. Securities and Exchange Commission (“SEC”), including the Company’s Annual Report on Form 20-F for the year ended December 31, 2024, and subsequent filings and reports filed with the AMF or SEC, or otherwise made public by the Company. References to the Company’s website and the AMF website are included for information only and the content contained therein, or that can be accessed through them, are not incorporated by reference into, and do not constitute a part of, this press release. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by the Company or any other person that the Company will achieve its objectives and plans in any specified time frame or at all. The Company undertakes no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. This press release and the information contained herein do not constitute an offer to sell or a solicitation of an offer to buy or subscribe to shares in Innate Pharma in any country. Summary of Interim Condensed Consolidated Financial Statements and Notes as of JUNE 30, 2025 Interim Condensed Consolidated Statements of Financial Position (in thousand euros) June 30, 2025 December 31, 2024 Assets Current assets Cash and cash equivalents 53,704 66,396 Short-term investments 6,323 14,374 Trade receivables and others 4,951 4,972 Total current assets 64,978 85,742 Non-current assets Property and equipment 4,955 5,133 Non-current financial assets 10,390 10,281 Other non-current assets 577 575 Trade receivables and others - non-current 12,036 9,328 Deferred tax asset — Total non-current assets 27,958 25,317 Total assets 92,937 111,059 Liabilities Current liabilities Trade payables and others 12,041 16,007 Collaboration liabilities – current portion 6,782 7,443 Financial liabilities – current portion 8,934 8,709 Deferred revenue – current portion 563 616 Provisions - current portion 1,106 207 Total current liabilities 29,426 32,982 Non-current liabilities Collaboration liabilities – non-current portion 34,518 41,128 Financial liabilities – non-current portion 18,095 22,286 Defined benefit obligations 2,666 2,730 Deferred revenue – non-current portion 2,628 2,825 Provisions - non-current portion 460 274 Total non-current liabilities 58,367 69,244 Shareholders’ equity Share capital 4,610 4,192 Share premium 407,048 390,979 Retained earnings (386,364) (336,893) Other reserves 1,194 27 Net income (loss) (21,344) (49,471) Total shareholders’ equity 5,144 8,834 Total liabilities and shareholders’ equity 92,937 111,059 Interim Condensed Consolidated Statements of Income (loss) (in thousand euros) June 30, 2025 June 30, 2024 Revenue from collaboration and licensing agreements 1,671 8,293 Government financing for research expenditures 3,189 4,052 Revenue and other income 4,860 12,345 Research and development expenses (20,520) (29,076) General and administrative expenses (9,767) (9,582) Operating expenses (30,287) (38,657) Operating income (loss) (25,427) (26,313) Financial income 6,886 3,613 Financial expenses (2,803) (2,064) Net financial income (loss) 4,083 1,549 Net income (loss) before tax (21,344) (24,764) Income tax expense — — Net income (loss) (21,344) (24,764) Weighted average number of shares : (in thousands) 86,937 80,872 - Basic income (loss) per share (0.25) (0.31) - Diluted income (loss) per share (0.25) (0.31) Interim Condensed Consolidated Statements of Cash Flow (in thousand euros) June 30, 2025 June 30, 2024 Net income (loss) (21,344) (24,764) Depreciation and amortization, net 707 1,142 Employee benefits costs 79 145 Change in provision for charges 1,085 (105) Share-based compensation expense 1,554 1,705 Change in fair value of financial assets (249) (992) Foreign exchange (gains) losses on financial assets 1,347 (524) Change in accrued interests on financial assets (191) (212) Disposal of property and equipment (scrapping) 20 18 Other profit or loss items with no cash effect 3 26 Operating cash flow before change in working capital (1) (16,989) (23,561) Change in working capital (14,175) 26,597 Net cash generated from / (used in) operating activities: (31,164) 3,036 Acquisition of property and equipment, net (58) (283) Purchase of other assets (3) — Disposal of current financial instruments and paid interests 7,143 1,215 Interest received on financial assets (108) — Net cash generated from / (used in) investing activities: 6,974 932 Proceeds from the exercise / subscription of equity instruments 14,932 93 Repayment of borrowings (4,456) (4,420) Net cash generated / (used in) from financing activities: 10,476 (4,327) Effect of the exchange rate changes 1,022 (257) Net increase / (decrease) in cash and cash equivalents: (12,692) (616) Cash and cash equivalents at the beginning of the year: 66,396 70,605 Cash and cash equivalents at the end of the six-months period: 53,704 69,989 (1) Cash flows from operating activities include an amount of €0.2 million of interests paid for the first half of 2025 (€1,3 million as of December 31, 2024) and interests received for €0,5 million for the first half of 2025 (€1,9 million as of December 31,2024). Revenue and other income The following table summarizes operating revenue for the periods under review: In thousands of euros June 30, 2025 June 30, 2024 Revenue from collaboration and licensing agreements 1,671 8,293 Government funding for research expenditures 3,189 4,052 Revenue and other income 4,860 12,345 Revenue from collaboration and licensing agreements Revenue from collaboration and licensing agreements decreased by €6.6 million, to €1.7 million for the six months ended June 30, 2025, as compared to revenues from collaboration and licensing agreements of €8.3 million for the six months ended June 30, 2024. These revenues mainly result from the partial or entire recognition of the proceeds received pursuant to the agreements with AstraZeneca and Sanofi. They are recognized when the entity's performance obligation is met. They are recognized at a point in time or spread over time according to the percentage of completion of the work that the Company is committed to carry out under these agreements. The evolution for the first half of 2025 is mainly due to: A €2.9 million decrease in revenue related to monalizumab, to €0.1 million for the six months ended June 30, 2024, as compared to €3.0 million for the six months ended June 30, 2023. This change is mainly due to the progress of Phase 1/2 trials close to termination. A €4.0 million decrease in revenue from the collaboration and research license agreement signed with Sanofi in 2016. On April 15, 2024, the Company announced the treatment of the first patient in the Phase 2 dose expansion part of the Sanofi-sponsored clinical trial evaluating NK Cell Engager SAR443579/ IPH6101 in various blood cancers. Under the terms of the 2016 agreement, this trial progress triggered a milestone payment of €4.0 million fully recognized in revenue during the first quarter of 2024. This amount was received by the Company on May 17, 2024. The Sanofi-sponsored Phase 1/2 clinical trial evaluating IPH6401/SAR'514 targeting BCMA in autoimmune indications, is on going. No milestone payment has been recognized as of June 30, 2025. Government financing for research expenditures Government financing for research expenditures decreased by €0.9 million, or 21.3%, to €3.2 million for the six months ended June 30, 2025 as compared to €4.1 million for the six months ended June 30, 2024. This change is mainly due to a €0.8 million decrease in the research tax credit due to a decrease in eligible subcontracting expenses. Operating expenses The table below presents our operating expenses for the six months periods ended June 30, 2025 and June 30, 2024: In thousands of euros June 30, 2025 June 30, 2024 Research and development expenses (20,520) (29,076) General and administrative expenses (9,767) (9,582) Operating expenses (30,287) (38,657) Research and development expenses Research and development (“R&D”) expenses decreased by €8.6 million, or 29.4%, to €20.5 million for the six months ended June 30, 2025, as compared to €29.1 million for the six months ended June 30, 2024, representing a total of 67.8% and 75.2% of the total operating expenses, respectively. R&D expenses include direct R&D expenses (subcontracting costs and consumables), depreciation and amortization, personnel expenses and other expenses. Direct R&D expenses decreased by €7.3 million, or 43.1%, to €9.7 million for the six months ended June 30, 2025, as compared to €17.1 million for the six months ended June 30, 2024. This variation is mainly explained by a €7.5 million decrease in expenses related to the phasing of studies (maturity of clinical studies on lacutamab, discontinuation of preclinical studies, and start of phase 1 of our antibody-drug conjugate (ADC) program). Expenditures related to preclinical programs increase by €0.2 million. The variation in clinical program expenses is explained by: (i) a €5.8 million decrease in preclinical costs for IPH4502 (drug manufacturing and toxicity studies) following the start of Phase 1; (ii) a €2.0 million euros decrease in the Lacutamab program (maturity of clinical studies) (iii) offset by a €0.4 million increase related to the IPH 65 program in the recruitment phase. Additionally, as of June 30, 2025, collaboration liabilities related to monalizumab and the agreements signed with AstraZeneca in April 2015, October 2018, and September 2020 amounted to €41.3 million, as compared to collaborations liabilities to €48.6 million as of December 31, 2024. This €7.3 million decrease mainly results from (i) net reimbursements of €1.7 million made to AstraZeneca in the first half of 2025 related to the co-funding of the monalizumab program, including the INTERLINK-1 Phase 3 trial launched in October 2020 and closed as of today and PACIFIC-9 launched in April 2022, and (ii) the decrease in the collaboration commitment by €5.6 million due to exchange rate fluctuations observed during the period for the euro-dollar exchange rate. Personnel and other expenses allocated to R&D decreased by €1.2 million, or 10.0%, to €10.8 million for the six months ended June 30, 2025, as compared to an amount of €12.0 million for the six months ended June 30, 2024. This decrease is attributable to other expenses of €1.1 million (primarily a reduction in scientific consulting fees due to the establishment of the clinical department, foreign exchange impacts, and lower patent royalties); (ii) depreciation and amortization charges of €0.4 million euros relating to Monalizumab rights following the full amortization of these rights, partially offset by an increase in personnel expenses as a result of the establishment of the clinical department. General and administrative expenses General and administrative expenses increased by €0.2 million, or 1.9%, to €9.8 million for the six months ended June 30, 2025, as compared to general and administrative expenses of €9.6 million for the six months ended June 30, 2024. General and administrative expenses represented a total of 32.2% and 24.8% of the total operating expenses for the six months ended June 30, 2025 and June 30, 2024, respectively. Personnel expenses includes the compensation paid to our employees. They amounted €4.8 million for the six months ended June 30, 2025, as compared to €4.0 million for the six months ended June 30, 2024. The increase of €0.8 million is mainly due to provisions for risks and charges. Non-scientific and consulting fees mainly consist of fees for statutory auditors, accountants, legal advisors, and recruitment. This item decreased by €0.5 million, or 27.8%, to €1.4 million for the first half of 2025, compared to €1.9 million for the first half of 2024. The decrease is mainly due to greater use of recruitment agencies in 2024 (for the establishment of the clinical department), which was not repeated in 2025. Other expenses remained stable. Financial income (loss), net We recognized a net financial income of €4.1 million in the six months ended June 30, 2025 as compared to €1.5 million in the six months ended June 30, 2024. This variance of €2.5 million mainly results from (i) a favorable variation in net foreign exchange gain increasing by €3.9 million for the first half of 2025 with its favorable impact on the collaboration liabilities recorded during the first half of 2025 in connection with the change in the dollar exchange rate and (ii) an unfavorable variation of €1.5 million in income resulting from financial assets and fair value revaluation due to an unfavorable effect of investment rates recorded on the financial markets. Balance sheet items Cash, cash equivalents, short-term investments and non-current financial assets amounted to €70.4 million as of June 30, 2025, as compared to €91.1 million as of December 31, 2024. Net cash as of June 30, 2025 amounted to €51.1 million (€72.1 million as of December 31, 2024). Net cash is equal to cash, cash equivalents and short-term investments less current financial liabilities. The Company also has bank borrowings of €26.4m, including €18.1m of State Guaranteed Loans (“Prêts Garantis par l’Etat”) as of June 30, 2025 and €8.3m loans subscribed with Société Générale for the construction of its head office as well as €0.6m of lease liabilities. The other key balance sheet items as of June 30, 2025 are: Deferred revenue of €3.2 million (including €2.6 million booked as ‘Deferred revenue – non-current portion’) and collaboration liabilities of €41.3 million (including €34.5 million booked as ‘Collaboration liabilities - non-current portion’) relating to the remainder of the initial payment received from AstraZeneca not yet recognized as revenue and the part of the co-financing of the monalizumab program with AstraZeneca; Receivables from the French government amounting to €10.7 million in relation to the research tax credit for 2024 and the six-month period ended June 30, 2025. Shareholders’ equity of €5.1 million, including the net loss of the period of €21.3 million and Sanofi investment for €15.0m. Cash-flow items As of June 30, 2025, cash and cash equivalents amounted to €53.7 million, compared to €66.4 million as of December 31, 2024, corresponding in a decrease of €12.7 million. The net cash flow used during the period under review mainly results from the following: Net cash flow generated from operating activities of €31.2 million for the six months ended June 30, 2025 as compared to net cash flows used by operating activities of €3.0 million for the six months ended June 30, 2024. Net cash flow from operating activities for the first half of 2024 notably includes (i) the collection of €15.0 million in January 2024 following Sanofi's decision to exercise one of its two license option for an NK Cell Engager program in solid tumors, derived from the Company's ANKET® (Antibody-based NK Cell Engager Therapeutics) platform, pursuant to the terms of the research collaboration and license agreement signed in December 2022, (ii) the collection in May 2024 of €4.8 million (including value-added tax) the treatment of the first patient in the Phase 2 dose expansion part of the Sanofi-sponsored clinical trial evaluating NK Cell Engager SAR443579/ IPH6101 in various blood cancers and (iii) the repayment by the French Treasury of the research tax credit receivable relating to the 2019 financial year for an amount of €16.7 million during the first quarter of 2024, as well as the carry-back receivable for an amount of €0.3 million. Restated for these transactions linked to collaboration agreements and other non-recurring items such as the CIR refund, net cash flow used in operating activities for the first half of 2025 decreased by €2.6 million as compared to the first half of 2024. This change mainly results from lower net payments to suppliers. Net cash flow from investing activities of €7.0 million for the six months ended June 30, 2025, as compared to net cash flow used in investing activities of €0.9 million for the first half of 2024. Net cash flow from investing activities for the first half of 2025 mainly composed of a disposal of current financial instruments to meet cash requirements and partially reinvested up to €4 million in term deposits in order to secure and diversify investments. Net cash flow from investing activities for the first half of 2024 is mainly composed of a disposal of a current financial instrument which generated a net cash collection of €1.2 million partially offset by acquisitions of property, plant and equipment and intangible assets for a net amount €0.3 million. The Company has not made any other investments in tangible, intangible or significant financial assets during the first half of 2025 and 2024. Net cash flow in financing activities for the six months ended June 30, 2025 was €10.5 million as compared to net cash flow used in financing activities of €4.3 million the six months ended June 30, 2024, This cash flow includes the investment for a net amount of €14,9 million received from Sanofi, partially offset by consumptions mainly related to repayments of financial liabilities for €4,4 million (€4,3 million for the six month ended June 30, 2024). Post period events Innate Pharma plans to prioritize its investment on what it believes are its highest-value clinical assets, IPH4502, lacutamab, and monalizumab partnered with AstraZeneca; its preclinical research and development (R&D) efforts will focus on advancing the next ADCs toward development, leveraging its pipeline of innovative targets. In line with such strategic focus and its objectives, the Company intends to streamline its organization. Staffing levels are expected to decrease overall by about 30%l, including through attrition. The planned layoffs will be implemented through a redundancy plan that is subject to consultation with the Workers’ Council and endorsement by the French authorities (Dreets). The implementation of the change is expected to be completed during the first half of 2026. Eric Vivier has decided to return to academic research full-time, and he will continue to support the Company’s innovation as an advisor to the R&D Committee of the Board of Directors. As Chief Operating Officer (COO), Yannis Morel will continue to be responsible for preclinical research and development, and will assume Chief Scientific Officer (CSO) responsibilities. Nota The interim condensed consolidated financial statements for the six-month period ended June 30, 2025 were established in accordance with IAS 34 standard adopted by European Union and as issued by the International Accounting Standards Board (IASB). They have been subject to a limited review by our Statutory Auditors and were approved by the Board of Directors of the Company on September 16, 2025. They will not be submitted for approval to the general meeting of shareholders. Risk factors Risk factors identified by the Company are presented in the item 3.D of the annual report filed with the SEC (20-F), on April 30, 2025 (SEC Accession No. 0001598599-25-000042). The main risks and uncertainties the Company may face in the six remaining months of the year are the same as the ones presented in the annual report available on the internet website of the Company. Of note, the risks that are likely to arise during the remaining six months of the current financial year could also occur during subsequent years. Related party transactions: Transactions with related parties during the periods under review are disclosed in Note 18 to the interim condensed consolidated financial statements for the period ended June 30, 2025 prepared in accordance with IAS 34.

摘要：MHC-E 作为一种高度保守的非多态性 MHC 分子，在先天和适应性免疫反应中发挥着关键作用。它能与自然杀伤细胞（NK 细胞）和 T 细胞上的抑制性及激活性受体相互作用，还可向 T 细胞受体呈递抗原。本文将从 MHC-E 的特性、调控的先天受体、在癌症中对先天受体的靶向应用、MHC-E 限制性适应性 T 细胞反应、诱导 MHC-E 限制性 T 细胞等方面，详细阐述这一分子在疫苗研发和免疫治疗中的巨大潜力，展现其为感染性疾病和癌症带来通用有效疗法的可能性。 一、MHC-E 的特性：免疫调控的保守分子1.1 MHC-E 的基本结构与功能 主要组织相容性复合体（MHC，人类中称为 HLA 复合体）在塑造细胞适应性和先天免疫反应中起着关键作用。MHC-I 区域包含编码经典 MHC-Ia 蛋白（如 MHC-A、MHC-B、MHC-C）和非经典 MHC-Ib 蛋白（如 MHC-E、MHC-F、MHC-G）的基因。其中，MHC-E（人类中为 HLA-E）是一种非多态性的 MHC-Ib 分子，具有独特的功能。 MHC-E 与经典 MHC-I 分子一样，由重链结合 β₂微球蛋白（β₂m）形成异二聚体，并与肽段结合。其特殊功能在于向 CD94-NKG2A 和 CD94-NKG2C 受体呈递保守的九肽（称为 VL9 肽），从而调节 NK 细胞和部分 CD8⁺T 细胞的活性。VL9 肽存在于 MHC-Ia 分子（以及 MHC-Ib 分子 HLA-G）的可切割信号序列中，在人类群体中最常见的 VL9 序列为（VM [A/P] PRT [V/l][L/V/l//F] L）。值得注意的是，HLA-E 自身并不包含 VL9 肽。1.2 MHC-E 的进化保守性与多态性 MHC-E 是灵长类动物中最保守的 MHC-I 基因座，在旧大陆和新大陆灵长类动物中都存在类似 HLA-E 的蛋白。在人类和非人灵长类动物中，MHC-E 的多态性非常有限。人类群体中仅发现两个主要等位基因，它们的差异仅在于 107 位氨基酸（HLA-E0101 中为 Arg；HLA-E01031 和 HLA-E*01032 中为 Gly）。这种多态性位于 HLA-E 的肽结合槽之外，不影响其结构，但会影响表面稳定性和表达水平。 在小鼠中，也存在类似的系统，非多态性的 MHC-Ib 蛋白 Qa-1b 同样结合保守的类 VL9 肽（称为 QDM，即 Qa-1 决定簇修饰物），这些肽由小鼠 MHC-Ia 分子的信号肽编码。因此，Qa-1b 是 HLA-E 在小鼠中的同源物，这种在细胞表面呈递 MHC-Ia 衍生肽的能力似乎是进化过程中高度保守的免疫防御机制。1.3 MHC-E 的表达与运输 与经典 MHC-Ia 分子类似，MHC-E 在大多数有核细胞上表达。但在大多数细胞上，MHC-E 的表面表达和 VL9 肽的呈递通常非常低，除非受到干扰素等炎症信号的诱导。此外，HLA-E 到达细胞表面后会迅速内化，其胞质尾将其导向晚期和循环内体。在没有干扰素诱导的情况下，HLA-E 的表面表达在白细胞亚群（如 T 细胞、NK 细胞、B 细胞、单核细胞和巨噬细胞）以及内皮细胞上最容易检测到。 HLA-E 的组装和细胞内运输有其特定过程（如图 1 所示）：HLA-Ia 分子是 I 型跨膜蛋白，其前导序列在通过 SEC61 复合体转运到内质网（ER）的过程中被信号肽酶（SPase）切割。VL9 肽包含在切割的前导序列蛋白片段中，该片段在 ER 膜上被信号肽肽酶（SPPase）进一步加工，并在释放到胞质中后被蛋白酶体加工。与经典 HLA-Ia 分子呈递的肽段类似，VL9 肽通过与抗原加工相关的肽转运蛋白（TAP）从胞质转运到 ER 腔，并以依赖于 tapasin 的方式装载到 HLA-E-β₂微球蛋白（β₂m）复合物上。此外，与抗原加工相关的 ER 氨肽酶（人类中的 ERAP1 和 ERAP2；小鼠中的 ERAAP）是 VL9 呈递所必需的，因为 ERAAP 敲除小鼠在 Qa-1b（HLA-E 的小鼠同源物）上呈递的肽段集合不同。 肽装载后，三聚体 VL9-HLA-E-β₂m 复合物通过高尔基体转运到细胞表面。然而，与经典 HLA-Ia 分子不同，由于其胞质尾中的内化信号，HLA-E 在细胞表面的周转迅速。同样，Qa-1b 也会从小鼠细胞表面迅速移除。HLA-E 的过量供应及其从细胞表面的快速周转可能提供了对细胞内 HLA-Ia 衍生 VL9 存在的实时监测，以便通过先天免疫受体进行持续感知。 图 1：HLA-E 的组装和细胞内运输过程二、MHC-E 调控的先天受体：免疫反应的开关2.1 CD94-NKG2A/NKG2C 信号通路 VL9 肽 - MHC-E-β₂m 复合物通过与 NK 细胞和 T 细胞上表达的抑制性和激活性先天受体结合，调节细胞的先天和适应性免疫反应。其中，表面暴露的 VL9 肽 - MHC-E-β₂m 三聚体复合物是异二聚体 I 型跨膜蛋白 CD94-NKG2A 和 CD94-NKG2C 的配体。这些受体是在所有脊椎动物物种中发现的进化上古老的 C 型凝集素谱系。 人类 CD94-NKG2A 是一种含免疫受体酪氨酸抑制基序（ITIM）的抑制性受体，而 CD94-NKG2C 是一种与免疫受体酪氨酸激活基序（ITAM）相关的激活性受体（如图 2 所示）。这些受体广泛表达于 NK 细胞，也存在于一些 CD8⁺记忆 T 细胞上，尽管它们在个体间的表达模式差异很大。 CD94-NKG2A 与 HLA-E 三聚体相互作用的结构分析揭示了 VL9 肽特异性的分子基础，也解释了为什么 NKG2A 与该复合物的亲和力高于 NKG2C。最近，小鼠 CD94-NKG2A 与结合肽 AMAPRTLLL 的 Qa-1b 结合的结构被解析，该结构揭示了与人类分子相比，配体 - 受体界面的细微差异，这解释了 CD94-NKG2A 与 HLA-E 或 Qa-1b 相互作用的物种特异性。基于这些结果，可以设计 Qa-1b 使其与人类 CD94-NKG2A 发生交叉反应。然而，总体而言，该结构证实了 MHC-E 系统在将源自经典 MHC-Ia 分子的自身肽呈递给 CD94-NKG2A 以调节 NK 细胞反应方面的显著保守性。2.2 LIR1 和 LIR2 信号通路 最近研究表明，抑制性受体白细胞免疫球蛋白样受体 1（LIR1）和 LIR2（也称为 LILRB1 和 LILRB2）与 Qa-1b 和 HLA-E 结合，且不依赖于结合的肽段（如图 2 所示）。因此，LIR1 可以被呈递非 VL9 肽的 HLA-E 分子激活，例如热休克蛋白 60（HSP60）信号序列中包含的肽段（在应激时上调），或人类蛋白质组中发现的其他与 HLA-E 强结合的肽段。除 HLA-E 外，LIR1 还与经典和其他非经典 MHC-I 分子以及病毒 MHC-I 样分子（如人类巨细胞病毒（HCMV）的 UL18）结合。LIR 与 HLA-E 相互作用的结构基础目前尚不清楚，但可能涉及 α3 结构域和 β₂m，正如在其他 LIR-MHC 复合物中观察到的那样。 图 2：HLA-E 的先天和适应性受体2.3 NK 细胞和 T 细胞反应的调节 与 CD8⁺αβT 细胞通过其 αβTCR 与肽 - MHC-I 复合物结合产生激活信号不同，NK 细胞通过大量激活性和抑制性受体的信号进行调节。这些受体在 NK 细胞发育和调节其在外周的活性中起着重要作用。同样，γδT 细胞可以通过其 γδTCR 与非 MHC 配体结合或通过激活性受体被激活。 在血液中，CD94-NKG2A 在大约一半的人类 NK 细胞、极少数循环 CD8⁺T 细胞（主要是先前激活的细胞）以及特定的 γδT 细胞亚群（δ2 亚群的 20-90%）上表达。在所有这些情况下，人们认为通过 NKG2A 的信号传导会抵消这些细胞在通过 TCR 或激活性受体激活时的即时效应功能，如细胞溶解。因此，CD94-NKG2A 在免疫激活后作为负反馈受体发挥作用，这可能在慢性感染期间维持 T 细胞功能和避免耗竭方面很重要。NKG2A 还与 NK 细胞的调节和 “教育” 以及通过避免激活诱导的细胞死亡来维持 NK 细胞克隆扩增有关。 γδT 细胞上 NKG2A 的表达增加了其在通过 γδTCR 或激活性受体信号传导时的激活阈值；阻断 NKG2A 可能会改善 γδT 细胞的抗肿瘤功能或其对抗慢性病毒感染（如 HIV 和乙型肝炎病毒）的活性。 据报道，只有一小部分 NK 细胞同时表达 NKG2A 和 NKG2C，且抑制性受体 NKG2A 与 MHC-E 的结合亲和力更高，因此如果同一 NK 细胞上同时表达这两种受体，抑制性信号通常会覆盖激活性信号。此外，CD94-NKG2A 和 CD94-NKG2C 的连接在很大程度上取决于 MHC-E 分子呈递的特定 VL9 序列。因此，人类 VL9 序列的多态性会影响 NK 细胞激活与抑制的阈值。 有趣的是，对 HLA-E 单链三聚体向 CD94-NKG2A 和 CD94-NKG2C 呈递随机肽段的酵母展示分析发现，在 CD94-NKG2A 选择的库和 CD94-NKG2C 选择的库之间，有一个高度保守的肽基序，以及与 NKG2A 结合亲和力高于 NKG2C 的肽段，反之亦然，这可能允许根据与 HLA-E 结合的肽序列特异性地激活或抑制 NK 细胞反应。似乎与 CD94-NKG2A 相比，CD94-NKG2C 对 VL9-HLA-E 的识别在 VL9 序列方面受到更多限制。2.4 对病原体的反应 表达激活性受体 NKG2C 的 NK 细胞比例在很大程度上取决于一个人是否感染了 HCMV。由于这些 NKG2C⁺NK 细胞在对某些病原体感染的反应中选择性扩增，它们被称为 “适应性” 或 “记忆” NK 细胞，尽管具有适应性特征的 NK 细胞也可以独立于 NKG2C 被诱导。除了高水平的 NKG2C 外，大多数适应性 NK 细胞都有表观遗传变化，包括减少转录因子 PLZF（也称为 ZBTB16）表达的高甲基化，以及随机抑制信号适配器 FcεRIγ、SYK 和 / 或 EAT2（也称为 SH2D1B）的表达，以及 IFNG 和 TNF 调控区域的低甲基化，这有助于这些细胞因子基因的转录。因此，适应性 NK 细胞对先天细胞因子（如 IL-12 和 IL-18，其受体被 PLZF 上调）以及某些 SLAM 蛋白和自然细胞毒性受体的刺激反应较差，但在 Fcγ 受体 FcγRIII（也称为 CD16）连接后产生高水平的干扰素 -γ（IFNγ）和 TNF，并介导增强的 Fcγ 受体依赖性抗体依赖性细胞毒性（ADCC）。 在慢性感染 HCMV 的个体中，适应性 NKG2C⁺NK 细胞群体的扩增部分可以通过 HCMV 糖蛋白 UL40 信号序列中存在的 VL9 模拟物来解释，这导致病毒感染细胞中 HLA-E 表面表达的强烈上调。非人灵长类动物巨细胞病毒也编码类似的蛋白，例如恒河猴巨细胞病毒（RhCMV）的 Rh67。有趣的是，不同 HCMV 株中 UL40 的 VL9 序列多态性反映了人类群体中 HLA 蛋白的 VL9 序列多态性。相比之下，Rh67 中的 VL9 序列没有多态性，这可能反映了非人灵长类动物 MHC 分子 VL9 序列缺乏多态性。与人类相似，恒河猴在 CMV 感染后适应性 NK 细胞群体也会扩增。 除了 UL40 中编码的 VL9 外，HCMV 蛋白 pp65 中编码的 HLA-E 结合肽段在体外已被证明能激活适应性 NK 细胞，但这些肽段是否在体内促进适应性 NKG2C⁺NK 细胞群体的扩增仍有待证实。 适应性 NK 细胞在慢性 HCMV 感染的个体中随时间产生。然而，在急性感染期间，HCMV VL9 肽的主要功能可能是通过抑制 NKG2A⁺NK 细胞来支持病毒免疫逃避，NKG2A⁺NK 细胞在适应性体液和细胞免疫反应之前代表第一道防线。在健康个体中，NKG2C⁺NK 细胞在控制 CMV 中的作用尚未明确确立，但有一些迹象表明，在 HCMV⁺移植受者中，NKG2C⁺NK 细胞水平高的人对 HCMV 感染的控制更好。此外，一项对肺移植受者的研究揭示，与患者 HLA-E 等位基因结合亲和力低的病毒 VL9 变体与随时间推移的高病毒载量相关。此外，NKG2C 缺陷已被证明是移植后 HCMV 介导的并发症的风险因素。 除 HCMV 外，其他病原体也被报道含有 HLA-E 结合肽段。然而，在大多数情况下，这些肽段导致 NK 细胞的刺激增强，而不是 NK 细胞逃避，因为肽 - HLA-E 复合物要么不与 NKG2A 结合，要么在某些情况下可以导致 NKG2C⁺NK 细胞的扩增。三、在癌症中靶向 MHC-E 的先天受体：免疫治疗的新方向3.1 NKG2C⁺NK 细胞用于癌症治疗 HLA-E 在肿瘤中的表达通常高于健康组织，在引起转移的循环肿瘤细胞上的表达甚至更高。同时，经典 MHC-Ia 分子通常下调，特别是在实体瘤中，而 HLA-G 可能上调。因此，表达 HLA-E 的癌细胞可以被适应性 NKG2C⁺NK 细胞靶向。相比之下，肿瘤浸润 T 细胞和 NK 细胞上 NKG2A 的表达会降低它们的抗肿瘤活性。因此，这一免疫检查点正被探索作为癌症免疫治疗的新靶点和提高癌症疫苗效力的手段。 适应性 NKG2C⁺NK 细胞被 VL9-HLA-E 复合物激活，而受结合的特定 VL9 序列（病毒或内源性）的影响最小。因此，存在于 HCMV⁺个体中的适应性 NK 细胞不仅能够攻击 HCMV 感染的细胞，还能攻击其他表达高水平 VL9-HLA-E 复合物的细胞，如某些肿瘤细胞。此外，适应性 NK 细胞具有强大的 ADCC 介导能力，这可能是由于它们减少了 FcεRIγ 的表达，这使得通过 FcγRIII 刺激对 IgG 的反应增强。 在急性髓系白血病（AML）患者中观察到了适应性 NK 细胞的这种有益 “副作用”，AML 是一种造血系统恶性肿瘤，其细胞表达高水平的 HLA-E。在接受富含 T 细胞和 NK 细胞的异基因造血干细胞移植的 AML 患者中，发现 HCMV 的再激活导致适应性 NK 细胞群体的扩增，这与 AML 复发的显著减少相关。适应性 NK 细胞在炎症条件下比其他 NK 细胞群体具有更强的抗凋亡能力，这在异基因造血干细胞移植环境中也可能是有利的。在 HCMV 再激活后获得的或来自诱导多能干细胞的 NKG2C⁺NK 细胞，也可以在体外使用抗 NKG2C-IL-15 - 抗 CD33 NK 细胞衔接器导向 AML 细胞，该衔接器将 NKG2C⁺NK 细胞导向 CD33⁺AML 细胞，同时通过 IL-15 为 NK 细胞提供增殖和存活信号（如图 3a 所示）。此外，适应性 NK 细胞对针对血液癌症（如多发性骨髓瘤）表面抗原的治疗性抗体触发的 ADCC 反应有重要贡献。 基于这些发现，有人假设可以使用从健康的 HCMV 血清阳性 “超级供体” 获得的 NKG2C⁺适应性 NK 细胞作为现成的治疗方法，用于血液系统癌症或其他 HLA-E 高表达的肿瘤，如某些胶质母细胞瘤。最近描述了一种符合良好生产规范的 NKG2C⁺适应性 NK 细胞富集和扩增方法，并且已经进行了多项使用现成适应性 NK 细胞输注的临床试验（如 NCT03081780、NCT03213964 和 NCT03319459）。另一种方法是使用 HLA-E 的肽配体，这些配体特异性刺激 NKG2C⁺NK 细胞但不刺激 NKG2A⁺NK 细胞。在肽库的无偏筛选和 HCMV 衍生肽的筛选中已经鉴定出这种 NKG2C 特异性肽配体。有可能使用这种 NKG2C 特异性肽在体内诱导适应性 NK 细胞反应。3.2 NKG2A 作为免疫检查点 尽管 HLA-E 的表达使癌细胞更容易受到 NKG2C⁺NK 细胞的攻击，但大多数肿瘤浸润 NK 细胞表达抑制性受体 NKG2A。因此，人们认为 HLA-E 的上调保护肿瘤免受 NK 细胞介导的控制。事实上，使用扩增的 NKG2A⁺NK 细胞进行的基因组规模 CRISPR 筛选表明，HLA-E 的表达是肿瘤细胞对 NK 细胞介导的细胞毒性敏感性降低的重要指标。已证明 NKG2A-HLA-E 相互作用是决定多种癌症中 NK 细胞介导的细胞毒性的关键因素，包括多发性骨髓瘤、慢性淋巴细胞白血病以及几种实体瘤（肾细胞癌、乳腺癌、肝癌、膀胱癌和肺癌，以及神经母细胞瘤和胶质母细胞瘤）。 此外，除了 NK 细胞外，很大一部分肿瘤浸润 CD8⁺T 细胞表达 NKG2A，通常与晚期分化和组织驻留标志物一起表达。肿瘤微环境中表达的 IL-12 似乎在 TCR 刺激后诱导 CD8⁺T 细胞上 NKG2A 表达方面起着关键作用。因此，癌细胞上的 HLA-E 表达，加上肿瘤微环境中 IL-12 的产生，会削弱肿瘤浸润 T 细胞的细胞溶解能力。首次报道 NKG2A 介导的 T 细胞激活抑制是针对黑色素瘤特异性 CD8⁺T 细胞的。从那以后，许多报道表明 HLA-E-NKG2A 像其他免疫检查点（如 PD-L1-PD1）一样，作为肿瘤特异性 CD8⁺T 细胞的免疫检查点发挥作用。因此，阻断 NKG2A 有可能 “解除” 肿瘤内 T 细胞和 NK 细胞的 “刹车”（如图 3a、b 所示）。 然而，在小鼠癌症模型中，单独阻断 NKG2A 对癌症进展几乎没有影响。相比之下，添加 NKG2A 阻断抗体增加了其他检查点抑制剂和癌症疫苗的效力。同样，在临床试验中使用 NKG2A 靶向单克隆抗体 monalizumab 阻断 HLA-E-NKG2A 轴作为单一疗法迄今为止效果甚微，但有报道称 monalizumab 与 PD-L1 阻断抗体联合使用在局部晚期（III 期）不可切除的非小细胞肺癌患者中取得了有希望的结果。一项正在进行的 III 期临床试验（NCT05221840）的结果预计在 2025 年底公布。 除了 monalizumab 外，其他 NKG2A 靶向抗体也在开发中。此外，靶向 VL9-HLA-E 的抗体也在开发中。这些可能具有以下优势：既阻断 NKG2A 介导的对 NK 细胞和 T 细胞反应的抑制，又触发 NK 细胞介导的对 HLA-E 表达肿瘤细胞的 ADCC。另一种防止 VL9-HLA-E 介导的对肿瘤靶向 T 细胞和 NK 细胞抑制的方法是靶向肿瘤细胞中 VL9 的加工和呈递途径，例如使用蛋白酶体阻断剂，已证明其可增加 NK 细胞对癌细胞的杀伤。在小鼠肿瘤模型中，最近表明通过删除肿瘤细胞中与抗原加工相关的 ER 氨肽酶（ERAAP）来改变 HLA-E 肽组，可阻止 NKG2A 的结合，并使肿瘤对 NK 细胞介导的控制敏感。此外，一种已被批准用于治疗多种癌症的 exportin-1 小分子抑制剂会影响 HLA-E 的表达，并增强 NK 细胞对白血病细胞的效应功能。靶向 VL9-HLA-E 的一个 caveat 是，这也会阻断 VL9-HLA-E 与激活性受体 NKG2C 的相互作用。3.3 修改细胞疗法中的 NKG2A 表达 HLA-E-NKG2A 抑制轴也已成为使用基因修饰 T 细胞或 NK 细胞进行有效过继细胞治疗的重要障碍。携带肿瘤抗原特异性 TCR 或嵌合抗原受体（CAR）的细胞毒性 T 细胞在癌症免疫治疗中显示出巨大前景，靶向 B 细胞标志物（主要是 CD19）的 CAR T 细胞已被批准用于治疗难治性 B 细胞恶性肿瘤。然而，CAR T 细胞在实体瘤治疗中显示出的疗效甚微，部分原因是免疫抑制性肿瘤微环境，包括 HLA-E 的上调。此外，CAR T 细胞在重新引入患者体内后可能会耗竭，导致抑制性受体（如 NKG2A）的上调。事实上，耗竭的 CAR T 细胞具有与 NK 细胞相似的特征，包括 NKG2A 的上调。由于 CAR T 细胞是通过体外基因修饰产生的，它们在体内向 NK 细胞样状态的转变可能通过靶向控制这种转变的关键转录因子或靶向负调节这些细胞激活的抑制性受体来预防。 此外，作为 CAR T 细胞的替代方案，可以使用携带 CAR 的基因工程 NK 细胞，这些 NK 细胞经过额外的基因修饰以降低或缺失抑制性受体的表达。例如，使用 CRISPR-Cas9 删除 KLRC1（编码 NKG2A），并通过慢病毒介导表达靶向 CD33 的 CAR，导致 CAR NK 细胞对 CD33⁺AML 细胞的杀伤活性增加（如图 3c 所示）。此外，这些 NKG2A 缺失的 CAR NK 细胞具有增加的 IFNγ 分泌，这反过来上调 HLA-E 的表达，从而可能使癌细胞更容易受到通过 NKG2C 刺激的适应性 NK 细胞的控制。然而，NKG2A 表达的沉默可能导致 CAR NK 细胞的存活率降低，因为通过 NKG2A 的信号传导也可防止激活诱导的细胞死亡。 一种创新的替代 NKG2A 缺失的方法是通过将含 ITIM 基序的胞质尾替换为 NKG2C 的胞质尾，将 NKG2A 转变为激活性受体，NKG2C 的胞质尾通过 DAP12 衔接蛋白的 ITAM 基序传递激活信号（如图 3c 所示）。这种 “A/C 开关” 方法利用了 NKG2A 与 HLA-E 的亲和力高于 NKG2C 的优势。转导这种 NKG2A-NKG2C 嵌合受体的 NK 细胞和 CD8⁺T 细胞在体外或小鼠模型中均可杀死 HLA-E 表达的肿瘤细胞，这取决于 HLA-E 的表达水平。由于仅靶向高 HLA-E 表达水平的细胞，这种方法预计具有有限的脱靶效应。因此，嵌合 NKG2A-NKG2C 受体代表了一种新型的 VL9-HLA-E 特异性 CAR。 图 3：靶向 HLA-E 表达的肿瘤细胞或感染细胞四、MHC-E 限制性适应性 T 细胞反应：免疫防御的另一维度4.1 病原体诱导的 MHC-E 限制性 T 细胞 除了通过先天受体调节 NK 细胞和 T 细胞反应外，HLA-E 还可以像 TCR 与经典 HLA-Ia 分子结合一样，被 CD8⁺T 细胞的 TCR 靶向，特别是当 HLA-E 呈递与内源性 VL9 肽不同的肽段时，T 细胞预计对这些肽段具有免疫耐受性。 人类中，巨细胞病毒（HCMV）是诱导 HLA-E 限制性 T 细胞的一个突出例子，因为 HCMV 的 UL40 蛋白编码的病毒 VL9 序列不仅作为 CD94-NKG2A 和 CD94-NKG2C 的配体发挥作用，还可以作为 HLA-E 限制性 CD8⁺T 细胞的靶标。事实上，HCMV 似乎诱导对 UL40-HLA-E 的长期效应记忆 T 细胞反应，其频率和表型通常与经典 HLA-Ia 限制性反应相当。当 UL40 衍生的 VL9 序列与内源性 VL9 前导序列不匹配时，UL40 特异性 HLA-E 限制性 T 细胞的频率似乎特别高。因此，这些 T 细胞有可能根据移植物中存在的内源性 VL9 序列促成同种异体移植物排斥。UL40-HLA-E 特异性 T 细胞不受 HCMV 对 MHC-Ia 依赖性抗原呈递的有效抑制的影响，这可能使它们在控制 HCMV 方面特别重要。HCMV 编码的 UL40 以不依赖于 TAP 的方式装载 MHC-E，这一特性在 RhCMV 编码的 Rh67 中是保守的，并由 VL9 序列上游的蛋白质序列介导。由于 UL40 VL9 肽的序列多样性有限，UL40-HLA-E 特异性 T 细胞的 TCR 多样性也可能有限，尽管比先天 NK 细胞或 NKT 细胞更多样。 UL40-HLA-E 特异性 T 细胞在控制 HCMV 感染中的作用仍在研究中。在肾移植受者中未观察到病毒 VL9 序列与 HCMV 负荷之间的相关性，而在儿童和母亲之间，UL40 衍生的和内源性 VL9 肽的不匹配被认为与先天性 CMV 疾病相关。然而，这些研究因 UL40 在调节 NK 细胞和 T 细胞反应中的双重作用而变得复杂。此外，最近的研究表明，具有对 UL40 衍生和内源性 VL9 肽均具有高亲和力的 TCR 的 UL40 反应性 T 细胞共表达 KIR2D 家族的抑制性 NK 受体，导致弱的功能反应，而具有低亲和力 TCR 的 VL9-HLA-E 特异性 T 细胞表达 NKG2C。因此，HLA-E 限制性 T 细胞识别似乎受到免疫耐受的中枢和外周机制的调节。 两种高分辨率结构提供了关于 TCR 与呈递 UL40 衍生 VL9 肽的 HLA-E 分子相互作用的进一步见解。值得注意的是，TCR 亲和力和 TCRβ 链的使用由 VL9 肽第 8 位的单个氨基酸决定。发现 TCR 与 HLA-E 的相互作用不同于 CD94-NKG2A 和 CD94-NKG2C，但类似于 TCR 与 HLA-Ia 分子的结合。尽管显示这两种 TCR 在 HLA-E 上具有不同的对接模式，但发现 TCR 相互作用的能量基础由一组保守的 HLA-E 残基定义，约一半的 HLA-E 接触残基对结合至关重要。这些研究共同表明 HLA-E 可以选择表达不同 TCR 的 T 细胞。 细胞表面的很大一部分 HLA-E 蛋白可能缺乏肽段，最近通过用识别无肽 HLA-E 的抗体染色也表明了这一点。这可能是 VL9 在细胞表面外出时从 HLA-E 解离的结果。与经典 MHC-Ia 分子不同，HLA-E 在没有肽段的情况下相当稳定。原则上，“空的” HLA-E 分子可以结合各种各样的非 VL9 肽，因为 HLA-E 的肽结合槽与其他 HLA-Ia 和 HLA-Ib 分子有一些相似之处。事实上，观察到 HLA-E 和 HLA-A2.1 的肽组之间存在一些重叠。与经典 MHC-Ia 分子类似，HLA-E、Mamu-E（恒河猴 HLA-E 的直系同源物）和 Qa-1b 结合在广泛的细胞蛋白质中发现的不同肽基序。然而，在表达 HLA-Ia 的细胞中，丰富的 HLA-Ia 衍生 VL9 配体通常会与其他要么频率较低要么与 HLA-E 结合较弱的细胞肽段竞争。相比之下，在缺乏 HLA-Ia 分子或 TAP 被抑制的细胞中表达的 HLA-E 分子可以洗脱非经典（非 VL9）配体。在 ERAAP 缺陷小鼠中或当小鼠 TAP 被病毒抑制剂阻断时，Qa-1b 装载有另一组可被 CD8⁺T 细胞识别的肽段。这些新的宿主蛋白衍生的 Qa-1b 结合肽段引起半不变的 CD8⁺T 细胞反应。小鼠 CMV 对 ERAAP 的抑制导致针对相同的主要 Qa-1b 限制性表位的 CD8⁺T 细胞反应。因此，尽管 HLA-E 限制性 T 细胞反应通常不是适应性免疫反应的主要部分，但它们可以在感染干扰抗原呈递的特定病原体期间被诱导。在每种情况下，非 VL9 肽如何获得尚不完全清楚，已经提出了几种通常是病原体特异性的途径（如图 4 所示）。 图 4：HLA-E 与非 VL9 肽的装载五、诱导 MHC-E 限制性 T 细胞：疫苗研发的新策略5.1 CMV 载体疫苗的发现 HLA-E 能够向 CD8⁺T 细胞呈递非 VL9 肽，这为将病原体和癌细胞用于逃避 NKG2A⁺NK 细胞反应的 HLA-E 上调转化为潜在弱点提供了独特机会。然而，尽管某些疫苗除了常规 CD8⁺T 细胞外，似乎还能诱导一些 HLA-E 限制性 T 细胞，但诱导针对特定病原体或癌症抗原的 HLA-E 限制性 CD8⁺T 细胞是疫苗开发的主要挑战。幸运的是，在非人灵长类动物巨细胞病毒（CMV）载体疫苗模型中的一个偶然发现可能提供了开发专门针对 HLA-E 而不是经典 HLA-Ia 分子的 CD8⁺T 细胞的疫苗的方法。 使用 CMV 作为疫苗载体的最初想法是基于观察到 CMV 在诱导和维持极高频率的效应记忆 T 细胞方面是独特的。有人假设，使用 CMV 诱导这种未耗竭的、循环的和组织驻留的 T 细胞，这些 T 细胞准备好快速发挥效应功能，可以防止难以控制的病原体（如 HIV）的初始传播。事实上，在恒河猴 HIV/AIDS 模型中，表达猿猴免疫缺陷病毒（SIV）抗原的 RhCMV 疫苗保护了约 60% 的恒河猴免受高致病性 SIVmac239 株的反复低剂量攻击。与常规疫苗载体相比，这种保护不仅更优越（如通过并列比较所示），而且在根本上不同，因为 SIV 的复制和传播在 SIV 攻击后早期被阻止，并且 SIV 最终从绝大多数受保护的猴子中清除。有趣的是，尽管 RhCMV-SIV 载体诱导的反应极其广泛，但它并未像其他 SIV 疫苗那样诱导针对相同表位的 CD8⁺T 细胞反应。相反，大约一半的 CD8⁺T 细胞受 MHC II 类限制，其余的受 MHC-E 限制。重要的是，这些 MHC-E 限制性 CD8⁺T 细胞不针对内源性或病毒编码的 VL9 肽，而是针对许多不同的、不相关的 SIV（和 RhCMV）肽，这表明它们与上述 CMV-VL9 特异性 HLA-E 限制性 T 细胞有根本不同。这些发现是前所未有的和令人惊讶的，因为自然感染的恒河猴具有受 MHC-Ia 限制的 RhCMV 特异性 CD8⁺T 细胞。 在 SIV 疫苗研究中使用的重组载体都基于源自 68-1 株的 RhCMV 克隆，与野生型 RhCMV 相比，该克隆包含多个基因突变、缺失和倒位。部分或完全修复其中一些缺失导致 RhCMV 载体诱导 MHC-Ia 限制性 T 细胞反应。因此，通过基因修饰 RhCMV 载体骨架，可以以相互排斥的方式编程针对不同 MHC 分子的 CD8⁺T 细胞反应，包括 MHC-E 限制性 CD8⁺T 细胞（MHC-II 限制性 CD4⁺T 细胞不受 RhCMV 68-1 株中任何遗传变化的影响）。正如最近综述的那样，在该模型中的广泛研究表明，RhCMV 编码 MHC-E 限制性 T 细胞启动的抑制剂和促进剂，包括几种趋化因子样蛋白，它们可以阻止 MHC-II 限制性和 MHC-E 限制性 T 细胞的诱导。从 RhCMV 或食蟹猴 CMV（CyCMV）的野生型样基因组中删除这些趋化因子样基因能够诱导非常规限制性 T 细胞。重要的是，当将 HCMV 编码的同源趋化因子样基因产物插入 RhCMV 68-1 株时，它们具有相同的抑制功能。此外，HCMV 特异性 MHC-I 同源物 UL18 是抑制性受体 LIR1 的配体，当插入 RhCMV 68-1 株时，也会阻止非常规限制性 CD8⁺T 细胞的诱导。这些结果共同表明，这种 T 细胞调节不仅限于非人灵长类动物 CMV。 人类和非人灵长类动物 CMV 都编码多种非常规（MHC-II 限制性和 MHC-E 限制性）T 细胞反应的抑制剂，这就提出了一个问题：为什么这些反应首先会被诱导（如表 1 所示）。尽管对于 MHC-II 限制性 T 细胞还没有答案，但似乎 MHC-E 限制性 T 细胞反应是 RhCMV Rh67 和 HCMV UL40 中编码的病毒 VL9 肽的副作用。删除 Rh67，甚至改变 Rh67 的 VL9 肽中的单个氨基酸，完全消除了 RhCMV 68-1 株诱导 MHC-E 限制性 CD8⁺T 细胞的能力，同时保持 MHC-II 限制性 CD8⁺T 细胞。重要的是，UL40 能够替代 Rh67 支持 MHC-E 限制性反应，再次支持这些机制在人类中的保守性。病毒 VL9 为什么以及如何需要诱导针对大量非 VL9 肽的 MHC-E 限制性 T 细胞尚不完全清楚，但由于在没有 Rh67 或 UL40 的情况下，由于病毒对 TAP 的抑制（阻止内源性肽的装载），MHC-E 保留在 ER 中，病毒 VL9 可能是 MHC-E 从 ER 输出所必需的，但最终被非 VL9 肽取代。然而，由于连同靶向 MHC 的病毒蛋白 Rh178、Rh182（或 US2）、Rh184（或 US3）和 Rh189（或 US11）一起删除病毒 TAP 抑制剂 Rh185（或 US6）并没有恢复 Rh67 缺失的 RhCMV 68-1 株诱导 MHC-E 限制性 T 细胞的能力，内源性 VL9 似乎不能替代病毒 VL9。因此，可能需要过量供应病毒 VL9 或 Rh67 和 UL40 的额外功能来诱导 MHC-E 限制性 CD8⁺T 细胞。病毒基因产物的大量存在阻止了病毒 VL9 表达的这种副作用，这让人想起 CMV 通过多基因逃避经典限制性 CD8⁺T 细胞，表明病毒在进化上有强烈的压力来避免经典和非经典 CD8⁺T 细胞反应。然而，尽管通过阻断 MHC-Ia 依赖性抗原呈递的细胞内蛋白在顺式中阻止了 MHC-Ia 限制性 CD8⁺T 细胞的刺激，但 CMV 感染细胞对 MHC-E 限制性 CD8⁺T 细胞的诱导似乎在反式中被趋化因子样蛋白的分泌或 MHC-I 样 HCMV 蛋白 UL18 的表面表达所阻止，UL18 通过 T 细胞上表达的抑制性受体 LIR1 抑制反应。 表 1：关于巨细胞病毒诱导的 MHC-E 限制性 T 细胞的关键问题及相关说明 通过在 CMV 载体中删除基因，可以对受 MHC-E、MHC-II 或 MHC-Ia 限制的 T 细胞反应进行编程，这一点通过将细胞类型特异性 microRNA 的靶向位点插入必需病毒基因中得到进一步扩展，从而限制病毒在相应细胞类型中的复制。携带髓系细胞特异性 microRNA 靶位点的 RhCMV 68-1 株因此不能在髓系细胞中复制，失去了诱导 MHC-E 限制性 T 细胞反应的能力，导致 “仅 MHC-II” 载体，而靶向内皮细胞特异性 microRNA 的位点导致 “仅 MHC-E” 载体。有趣的是，在 RhCMV 68-1 载体中同时包含髓系细胞特异性和内皮细胞特异性 microRNA 靶位点，会使 CD8⁺T 细胞反应恢复为 MHC-Ia，这表明当细胞类型特异性非常规启动被阻止时，常规 MHC-Ia 限制是默认的启动模式。然后，使用不同的 RhCMV 骨架，可以确定哪种 CD8⁺T 细胞程序在保护对抗 SIV 方面最有效。多项研究结果表明，只有诱导 MHC-E 限制性 CD8⁺T 细胞的载体（单独或与 MHC-II 限制性 CD8⁺T 细胞一起）才能保护对抗 SIVmac239 攻击。这是首次证明在没有 MHC-Ia 限制性 CD8⁺T 细胞的情况下，MHC-E 限制性 CD8⁺T 细胞在疫苗中具有保护性。 使用 RhCMV 或 CyCMV 载体的疫苗不仅已显示出对 SIV 的保护作用，还对结核分枝杆菌（Mtb）、疟原虫疟原虫和高致病性禽流感病毒有保护作用。与 SIV 不同，MHC-E 限制性 T 细胞在保护对抗 Mtb 方面并不优于 MHC-Ia 限制性 T 细胞，并且对抗流感病毒的保护与 CD4⁺T 细胞反应而非 CD8⁺T 细胞反应相关。对于疟疾，“仅 MHC-Ia” 载体是否具有保护性尚未确定。Mtb 的结果表明，Mtb 自然诱导的 HLA-E 限制性 CD8⁺T 细胞可能不具有保护性。在恒河猴中，还针对乙型肝炎病毒和已确立的癌症抗原诱导了 MHC-E 限制性 T 细胞。后一项发现特别引人注目，因为许多癌症抗原是自身抗原，由于中枢耐受，通常难以诱导强烈的 MHC-Ia 限制性 CD8⁺T 细胞反应。重要的是，在这两种情况下，表明恒河猴中的 MHC-E 限制性 T 细胞对表达靶抗原和 HLA-E 的人类细胞有反应，这与 Mamu-E 和 HLA-E 之间肽结合槽的高度保守性一致。 针对源自病原体或癌细胞的特定表位或整个抗原的 HLA-E 定向疫苗诱导 T 细胞可能比传统的基于 T 细胞的疫苗更有优势，因为特定病原体或癌症尚未被选择来逃避这些类型的 T 细胞，因此可能容易受到它们的控制，特别是当 HLA-E 被上调以限制 NK 细胞介导的控制时。在 RhCMV-SIV 模型中就是如此，其中 MHC-E 限制性 T 细胞赋予了与任何其他疫苗不同的保护类型。鉴于常规 HIV 疫苗的历史基本上是失败的，诱导 MHC-E 限制性反应的疫苗可能为防止 HIV 在人群中继续传播提供希望。同样，在许多癌症中观察到的 HLA-E 上调可能使它们特别容易受到 HLA-E 限制性 T 细胞的控制。 然而，在人类中开发诱导 MHC-E 限制性 T 细胞的疫苗并非没有挑战。基于 CMV 的疫苗面临的障碍是，CMV 在感染和持续存在的能力以及诱导 MHC-E 限制性 CD8⁺T 细胞的能力方面具有高度的物种特异性。因此，基于 HCMV 的 HIV 疫苗经过基因修饰，与非人灵长类动物 CMV-SIV 疫苗的修饰同源，目前正在临床测试中（NCT05854381 和 NCT04725877）。或者，基于非人灵长类动物 CMV 的疫苗可以在人类中进行测试，前提是能够解除 MHC-E 限制性 T 细胞启动的物种特异性限制，这是正在进行的研究的目标。另一种可能性可能是开发模拟 CMV 诱导的抗原呈递途径和 compartments 变化的 DNA 或 mRNA 疫苗，这些变化有利于 MHC-E 限制性 T 细胞的启动。令人鼓舞的是，最近已显示其他疫苗部分诱导 MHC-E 限制性 T 细胞，包括 mRNA 和腺病毒载体疫苗。然而，这些方法不太可能诱导以 MHC-E 限制性 T 细胞为主并靶向大量表位的 T 细胞反应。因此，基于传统疫苗的 MHC-E 限制性 T 细胞诱导可能仅限于特定表位。这种基于表位的疫苗的一个特别挑战是非 VL9 肽与 MHC-E 的低结合效率。虽然 VL9 肽稳定 HLA-E 分子，但在各种测定中通常无法检测到非 VL9 肽的结合。5.2 MHC-E 限制性 T 细胞的治疗潜力 越来越多的证据表明，呈递非 VL9 肽的非多态性 HLA-E 分子可以被 HLA-E 限制性 T 细胞靶向，这为新型免疫疗法提供了令人兴奋的机会。HLA-E 有限的多态性是开发针对传染病或癌症的现成 TCR-based 免疫疗法的一个特别有吸引力的特征。传统的 TCR 转染 T 细胞或含 TCR 的可溶性免疫试剂（如双特异性抗体）的使用仅限于表达与该 TCR 限制的匹配 HLA-Ia 等位基因的受者。相比之下，HLA-E 限制性 TCR 没有这种限制，因此可以普遍使用，无论受者的 HLA 类型如何。与传统的基于 TCR 的试剂一样，如果给定的靶抗原在非癌组织中表达，或者给定的病原体表位特异性 TCR 与宿主蛋白的表位交叉反应，HLA-E 限制性 TCR 可能会产生脱靶效应，尽管在没有炎症的情况下，健康组织中 HLA-E 的低表达水平可能会限制脱靶 TCR 触发。 尽管具有潜在优势，但开发靶向 HLA-E 的 TCR 仍面临挑战，因为许多传统的 TCR-MHC 相互作用规则似乎不适用于 HLA-E 限制性 TCR 识别。如上所述，几乎所有非 VL9 肽都与 HLA-E 结合不太紧密。这使得难以通过传统的免疫肽组学方法鉴定这些肽，也限制了它们在通过四聚体或五聚体染色鉴定特定 T 细胞和 TCR 方面的用途。一种更成功的方法似乎是对特定抗原的 HLA-E 结合肽进行生物信息学预测，然后验证肽 - HLA-E 结合，然后从受感染个体或体外启动的培养物中克隆识别这些肽在 HLA-E 背景下的 T 细胞和 TCR，或者筛选合成 TCR 库以鉴定肽 - HLA-E 反应性 TCR。然而，TCR-MHC-E 相互作用似乎也具有低亲和力，即使亲和力成熟也无法克服这一问题，从而限制了可溶性 TCR-based 试剂的实用性。需要调整这些方法以允许靶向低亲和力相互作用，才能成功应用现成的基于 TCR 的方法。六、结论 在过去十年中，由于一系列发现，HLA-E 已从一个模糊的免疫调节细节转变为在免疫疗法开发中具有核心作用。HLA-E 作为先天受体的配体和抗原呈递蛋白的双重性质为治疗和预防干预提供了无数可能性。尽管大多数方法仍处于临床前阶段，但几种新的治疗方法和疫苗现在正在传染病和癌症的临床试验中进行测试。许多实验室的工作使这一进展成为可能，我们预计未来几年将产生涉及 HLA-E 的新的令人兴奋的临床前和临床数据。 识别微信二维码，添加抗体圈小编，符合条件者即可加入抗体圈微信群！ 请注明：姓名+研究方向！ 本公众号所有转载文章系出于传递更多信息之目的，且明确注明来源和作者，不希望被转载的媒体或个人可与我们联系(cbplib@163.com)，我们将立即进行删除处理。所有文章仅代表作者观点，不代表本站立场。