Rakuten Medical is developing and commercializing its proprietary Alluminox® platform‑based photoimmunotherapy, which employs an antibody–dye conjugate that is photoactivated by focal red light. This article reviews the scientific rationale, mechanism of action, translational development, and emerging clinical evidence supporting the Alluminox platform-based photoimmunotherapy, with a focus on ASP‑1929, an EGFR‑targeted photoimmunotherapy currently under global Phase 3 evaluation in recurrent head and neck squamous cell carcinoma (HNSCC). Together, the data illustrate how integrated drug–device co‑development may expand the therapeutic scope of targeted oncology beyond traditional ADC design.
Photoimmunotherapy: A Targeted Modality Enabled by Controlled Light Activation
Achieving selective tumor eradication while sparing surrounding normal tissue remains a fundamental challenge in oncology. Conventional molecular‑targeted therapies, including antibody‑based approaches, often depend on sustained systemic exposure, which can limit therapeutic selectivity. Photoimmunotherapy (PIT) was developed to address this limitation by decoupling tumor targeting from cytotoxic activation.
Photoimmunotherapy is a drug–device combination therapeutic modality in which a cell-targeting moiety, such as a monoclonal antibody, is conjugated to a photoactivatable dye that remains biologically inert until externally activated by light using medical devices. This two‑step mechanism—antigen‑specific binding followed by localized light exposure—enables spatial and temporal control over cytotoxicity that is not achievable with conventional ADCs or small‑molecule therapies.
Rakuten Medical is currently developing drug conjugates using IRDye® 700DX (IR700), a hydrophilic silicon phthalocyanine dye, which is protected by intellectual property (IP) covering manufacturing technologies, clinical applications, and IR700 dye-conjugate compositions. In ASP‑1929, IR700 is conjugated to cetuximab to target the epidermal growth factor receptor (EGFR). Following intravenous administration, the antibody–IR700 conjugate selectively binds EGFR‑expressing tumor cells and remains inactive in the absence of light.
Cytotoxic activity is induced only after exposure to 690 nm red light. Preclinical studies have shown that illumination of antibody‑bound cells triggers rapid plasma membrane damage, resulting in necrotic cell death without requiring conjugate internalization. This light‑dependent mechanism confers high target selectivity, as cytotoxicity occurs only where antibody binding and light exposure coincide, forming the mechanistic basis for clinical translation.
Further detailed investigations have been conducted into the mechanism of action of photoimmunotherapy, and these studies have shown that photoexcitation of IR700 generates reactive oxygen species, leading to cell death via damage to the cell membrane and subcellular lysosomes. Additional factors, such as the aggregation of IR700 leading to structural changes and the tumor’s oxygen environment, have also been suggested to be involved in the mechanism of action.
The core photoimmunotherapy technology was discovered at the U.S. National Institutes of Health (NIH) and subsequently licensed to Rakuten Medical for clinical development.
Recently, Rakuten Medical announced the provision of its IR700 at an administrative fee-only acquisition cost for academic research with increased flexibility for publication, IP and commercialization opportunities. By expanding academic access under more flexible terms for research, publication and innovation, Rakuten Medical aims to accelerate the development of new treatment technologies and contribute meaningfully to advances in global healthcare. [1][2][3][4][5][6][7]
RM‑1929‑101: First‑in‑Human Evaluation of EGFR‑Targeted Photoimmunotherapy
The RM‑1929‑101 Phase 1/2a, open‑label, multicenter study evaluated the safety and preliminary efficacy of EGFR‑targeted photoimmunotherapy in patients with locoregional recurrent HNSCC who were not candidates for curative surgery, radiation, or platinum‑based chemotherapy. Results were reported in the peer‑reviewed journal Head & Neck.
RM‑1929, a cetuximab–IRDye® 700DX conjugate, was administered intravenously, followed by local red‑light illumination to activate the drug at the tumor site. The study comprised a dose‑escalation phase and a Phase 2a expansion. No dose‑limiting toxicities were observed, and a dose of 640 mg/m² with fixed light parameters was selected for further evaluation.
In the Phase 2a cohort of 30 heavily pretreated patients, treatment was generally tolerated. Grade ≥3 adverse events occurred in 63.3% of patients, consistent with the advanced disease setting; reported deaths were assessed as not treatment‑related. Preliminary antitumor activity was observed, with a confirmed objective response rate of 26.7% and a median overall survival of 9.3 months.
Based on the totality of safety and efficacy data generated in RM‑1929‑101 and related clinical experience, ASP‑1929—an analogous formulation with comparable physical and chemical properties—received approval in Japan under the Sakigake Designation System and the Conditional Early Approval System for unresectable locally advanced or recurrent head and neck cancer. The approval represents the world’s first, and to date only, regulatory approval of a photoimmunotherapy‑based drug–device combination.[8]
Real-World Evidence and Clinical Outcomes
Real‑world evidence from post‑approval use of photoimmunotherapy for head and neck cancer in Japan has provided insight into its clinical activity, safety, and functional impact in routine practice. In a multicenter retrospective study of 40 patients with unresectable locally advanced or locally recurrent head and neck cancer, the primary endpoint of time to treatment failure (TTF) was 6.0 months, supporting the role of photoimmunotherapy as a local control–oriented modality in this setting. Median progression‑free survival (PFS) was 6.2 months and median overall survival (OS) was 26.9 months. Antitumor activity was observed, with an objective response rate (ORR) of 75.0% and a disease control rate (DCR) of 95.0%.
Consistent findings were reported in a single‑center retrospective analysis of 45 patients comparing photoimmunotherapy (n = 22) with contemporaneous systemic pharmacotherapy (n = 23). Median OS was 35 months in the photoimmunotherapy group versus 8 months in the pharmacotherapy group; however, the authors note that baseline characteristics differed between groups and that selection bias could not be fully avoided, precluding definitive attribution of the OS difference to a direct treatment effect. Among patients treated with photoimmunotherapy, complete responses (CR) occurred in 31.8% and partial responses (PR) in 50.0%, yielding an ORR of 81.8% and a DCR of 90.9%, compared with an ORR of 39.1% in the pharmacotherapy group.
Across real‑world cohorts, the safety profile of photoimmunotherapy was consistent with prior clinical experience. Local adverse events, such as pain and mucositis, were common but generally manageable, whereas grade ≥3 adverse events occurred infrequently. These findings reflect the localized nature of the therapy and its limited systemic exposure.
Beyond tumor response, preservation of quality of life (QoL) is a critical consideration in head and neck cancer. In a prospective real‑world QoL analysis, patient‑reported QoL measures showed no clinically meaningful deterioration when assessed before treatment and four weeks after photoimmunotherapy, despite local treatment‑related effects. In this cohort, an overall response rate (89%) was observed alongside stable QoL outcomes, leading the authors to conclude that photoimmunotherapy provided effective local control without compromising functional status. [9][10][11]
ASP1929-181: Combining Photoimmunotherapy with Pembrolizumab
Preclinical studies have shown that cancer cell targeting photoimmunotherapy reshapes the tumor microenvironment to favor antitumor immunity, increasing infiltration of effector CD8+ T cells and synergizing with anti-PD-1 therapy to achieve durable tumor control. Photoimmunotherapy may therefore serve as a local immune-priming modality that enhances responsiveness to checkpoint blockade.
Building on these findings, ASP‑1929 photoimmunotherapy was evaluated in combination with pembrolizumab in the open‑label ASP‑1929‑181 Phase Ib/II study in patients with recurrent and/or metastatic HNSCC. An interim analysis of the HNSCC cohort was reported in Head & Neck with a data cut‑off of April 30, 2024.
Nineteen patients were enrolled, and 18 were evaluable for efficacy. The objective response rate was 27.8%, including a confirmed complete response rate of 22.2%, with a disease control rate of 61.1%. Responses occurred early (median time to response, 1.4 months), and all confirmed complete responses were durable and ongoing at the time of analysis. Median overall survival was 25.6 months, although follow‑up was ongoing.
The safety profile of the combination was consistent with that of each component therapy, with no new or unexpected toxicities observed. Exploratory translational analyses demonstrated increased CD8⁺ T‑cell density and reduced EGFR expression in treated lesions, findings consistent with photoimmunotherapy‑associated immune activation and supportive of the biological rationale for combination with PD‑1 blockade.
Taken together, the ASP‑1929‑181 results suggest that localized, light‑activated tumor cell killing may contribute to both direct antitumor effects and modulation of the tumor immune microenvironment, providing a mechanistic framework for continued evaluation of photoimmunotherapy‑based combinations in HNSCC. [12]
ASP‑1929‑381: Ongoing Global Phase 3 Program
ASP‑1929‑381 (NCT06699212) is an ongoing global Phase 3, randomized, open‑label trial evaluating ASP‑1929 photoimmunotherapy in combination with pembrolizumab versus pembrolizumab‑based standard of care as first‑line treatment for patients with locoregional recurrent HNSCC without distant metastases, as described in an ASCO Trial‑in‑Progress abstract.
The study is specifically focused on patients with recurrent disease who are candidates for pembrolizumab-based therapy and have at least one lesion accessible for light illumination. By targeting locoregional recurrence—an important contributor to morbidity and mortality in HNSCC—the trial is positioned to assess whether enhanced local tumor control may translate into improved clinical outcomes in this setting.
The study assesses overall survival as the primary endpoint and incorporates translational biomarker analyses to further characterize immune modulation. More than 30 clinical sites across the United States, Taiwan, Japan, and Ukraine are currently enrolling patients. [13]
Based on trial results, Rakuten Medical aims to submit a Biologics License Application (BLA) to the U.S. FDA in 2028.
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Clinical trials
A Study of ASP-1929 Photoimmunotherapy in Combination With Pembrolizumab in First-line Treatment of Locoregional Recurrent Squamous Cell Carcinoma of the Head and Neck With No Distant Metastases (ECLIPSE) – ClinicalTrials.gov ID NCT06699212
Reference
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[9] Okamoto I, Hasegawa O, Kushihashi Y, et al. Real‑world effectiveness and safety of photoimmunotherapy for head and neck cancer: a multicenter retrospective study. Cancers (Basel). 2025;17(16):2671.[Article]
[10] Tahara H, Ueda T, Hattori T, et al. Outcomes of near‑infrared photoimmunotherapy for head and neck cancer: a single‑center retrospective study. Cancers (Basel). 2026;18(3):350.[Article]
[11] Okamoto I, Okada T, Tokashiki K, Tsukahara K. Quality‑of‑life evaluation of patients with unresectable locally advanced or locally recurrent head and neck carcinoma treated with head and neck photoimmunotherapy. Cancers (Basel). 2022;14(18):4413. [Article]
[12] Cognetti DM, Gillenwater AM, Maniakas A, et al. Safety and efficacy findings from a Phase Ib/II study of ASP‑1929 photoimmunotherapy with pembrolizumab in recurrent and/or metastatic head and neck squamous cell carcinoma. Head Neck. 2024.[Article]
[13] Maniakas A, Gillenwater AM, Cognetti DM, et al. ASP‑1929 photoimmunotherapy plus pembrolizumab for locoregional recurrent head and neck squamous cell carcinoma: trial‑in‑progress. J Clin Oncol. 2025;43(16_suppl):TPS6122.[Article]
Featured image: NIR-PIT NCI Rakuten. Photo courtesy: © 2016 – 2026 Rakuten Medical, Inc. Used with permission.
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