Shionogi and F2G Report Positive Top Line Data from Phase III OASIS Study

Shionogi and F2G's Olorofim Achieves Phase III Primary Endpoint

Shionogi and F2G announced positive top-line results from their global Phase III OASIS study, evaluating the oral antifungal drug olorofim for adults with invasive aspergillosis whose infection is refractory to or unsuitable for azole therapy. The study successfully met its primary endpoint, demonstrating non-inferiority for olorofim compared to AmBisome followed by standard of care (SOC). Olorofim showed an all-cause mortality (ACM) rate of 23.8% at day 42, closely matching AmBisome/SOC's 24.3%, with a difference of -0.5% (95% CI: -13.1% to 10.8%). The drug also exhibited a favorable safety profile, with fewer drug-related treatment-emergent adverse events (35.8% vs 63.9% for AmBisome/SOC), primarily due to fewer renal events.

• The OASIS Phase III study successfully achieved its primary endpoint, demonstrating olorofim's non-inferiority to AmBisome followed by standard of care in treating invasive aspergillosis. The all-cause mortality rate at day 42 for olorofim was 23.8%, which was comparable to 24.3% for the comparator arm, indicating similar efficacy in a patient population with limited treatment options.
• Olorofim showed a significantly better safety profile compared to AmBisome and SOC, with drug-related treatment-emergent adverse events reported in 35.8% of olorofim patients versus 63.9% in the comparator arm. This difference was largely attributed to a lower incidence of renal events with olorofim, addressing a critical challenge in current antifungal treatments.
• Following these positive results, F2G plans to submit the data to regulatory authorities in the US, while Shionogi will handle submissions in Europe and Asia. The drug previously received breakthrough therapy designations from the US FDA based on Phase IIb data, underscoring its potential as a new treatment option for patients with invasive aspergillosis, an area with high unmet medical need.

Olorofim's Positive Phase III OASIS Results for Invasive Aspergillosis

Recent clinical evidence on invasive aspergillosis spans a range of study designs — from pediatric trials to retrospective multicenter analyses — reflecting the breadth of unmet needs across patient populations. The studies below highlight key interventions evaluated in 2025–2026, with notable findings on both efficacy and safety.

• Phase 2 Pediatric Posaconazole Trial (NCT04218851, 2026): An open-label, noncomparative, multinational trial enrolling 31 pediatric patients (ages 2–<18 years; weight ≥10 kg) with possible, probable, or proven invasive aspergillosis. Intervention consisted of IV posaconazole for ≥1 week with optional transition to oral formulation (tablet or suspension) over a total 12-week course, using weight-based dosing. Favorable global clinical response rates were 67.7% (95% CI: 48.6–83.3) at week 6 and 77.4% (95% CI: 58.9–90.4) at week 12, with no relapses observed; Day 114 all-cause mortality was 12.9%. Safety was favorable: 22.6% of participants experienced ≥1 treatment-related adverse event (TRAE), all grade 1 or 2 and fully resolved, with only one discontinuation due to a nonserious TRAE.

• Olorofim Phase IIb Study (Study 32, NCT03583164, 2025): An open-label, single-arm Phase IIb trial evaluating olorofim versus salvage therapy (external control arm) in patients with proven or probable invasive aspergillosis and limited treatment options. A cost-effectiveness analysis conducted from a US payer perspective using a hybrid decision tree–Markov model (one-year time horizon) found olorofim generated 0.46 QALYs versus 0.22 for salvage therapy, at one-year costs of $167,971 versus $208,696, yielding an incremental cost reduction of $40,725. Olorofim was the dominant strategy, with an incremental net monetary benefit of $52,827; probabilistic sensitivity analysis confirmed dominance in 90.0% and cost-effectiveness in 97.5% of 1,000 iterations.

• Multicenter Retrospective L-AmB versus Triazoles Study (2026): A 10-year retrospective study at two academic hospitals evaluating liposomal amphotericin B (L-AmB, n=105) versus mold-active triazoles (n=296) as primary therapy in 401 adult patients with proven or probable invasive aspergillosis (median age 65 years; 60.8% male). Ninety-day survival rates were comparable between groups: triazoles 58.8% (95% CI: 53.4–64.7) versus L-AmB 53.3% (95% CI: 44.6–63.8; P=0.3), with IPTW-adjusted hazard ratio of 1.43 (95% CI: 0.87–2.33; P=0.61). Patients on L-AmB were significantly more likely to have therapy changed (63.8% vs. 17.2%; P<0.001), predominantly switching to oral triazoles (71.6%), while adverse events drove 45.1% of triazole switches.

• ECMM Multicenter Biomarker Study (2026): A prospective multicenter study by the European Confederation of Medical Mycology enrolling 51 patients with probable or proven invasive aspergillosis and underlying hematological malignancies. Serial serum samples were analyzed over three weeks using the Olink Target 96 Inflammation panel. During the first days of treatment, all significantly differentially expressed proteins were upregulated in patients with clinical improvement versus worsening disease (except CCL23), and multiple proteins correlated with the need to switch to salvage antifungal therapy. MMP-10 emerged as a predictor of late treatment response, and low serum concentrations of CXCL6 (week 2) and MMP-10 (week 3) were associated with higher survival probability.

• Isavuconazole Literature Review Study (2026): A retrospective case series of two patients with acute invasive fungal rhino-sinusitis caused by Mucor (2022–2025), supplemented by a PubMed literature review of 387 cases (2011–2025) spanning Mucor and Aspergillus infection groups. Isavuconazole monotherapy achieved an efficacy rate of 89.47%, significantly exceeding amphotericin B monotherapy (59.68%; p<0.05); isavuconazole combination therapy reached 86.67% efficacy, also significantly superior to amphotericin B monotherapy (p<0.05). The overall efficacy of isavuconazole was found to be comparable to voriconazole (p<0.05), supporting its role as a viable alternative in both invasive aspergillosis and mucormycosis.

The Persistent Challenges in Treating Invasive Aspergillosis

Despite decades of antifungal drug development, invasive aspergillosis (IA) remains a disease associated with substantial morbidity and mortality, with clinical response rates achievable by even the newest therapies reaching only approximately 50% and mortality exceeding 50% in many patient populations. The therapeutic landscape is constrained not only by the inherent limitations of available drug classes but also by evolving resistance patterns, complex pharmacology, and persistent gaps in evidence-based guidance for optimal treatment strategies.

• Triazole limitations: Although azoles represent the only orally bioavailable antifungal class for IA, their clinical utility is frequently compromised by significant toxicities, pharmacokinetic variability, drug–drug interactions, and increasing rates of acquired and intrinsic resistance. Breakthrough infections with resistant Aspergillus species are becoming a growing clinical concern, particularly in patients requiring prolonged antifungal therapy.

• Echinocandin and amphotericin B constraints: Echinocandins offer a favorable safety profile and low drug interaction potential, but remain unvalidated as monotherapy for IA, limiting their role to salvage or combination regimens. Amphotericin B preparations, while broadly active, carry significant nephrotoxicity and systemic toxicity burdens that necessitate intensive patient monitoring.

• Unresolved evidence base for combination therapy: Despite the theoretical rationale for antifungal combinations, clinical trials have not demonstrated a clear benefit of combination regimens over voriconazole monotherapy, and critical questions regarding optimal combination strategies remain unanswered by evidence-based data.

• Diagnostic and treatment initiation challenges: Diagnosis of IA continues to be difficult and frequently delayed, complicating timely therapeutic decision-making. Evidence-based guidelines provide strong initial guidance but cannot address all nuanced management scenarios encountered in clinical practice.

• Lagging clinical trial infrastructure: Relative to therapeutic areas such as oncology or HIV, the clinical trial framework investigating optimal antifungal combinations and treatment durations for IA remains underdeveloped, leaving fundamental questions about best-practice management unresolved.

Positioning Olorofim Against Current Invasive Aspergillosis Therapies

The therapeutic landscape for invasive aspergillosis (IA) has evolved considerably over the past two decades, with voriconazole displacing amphotericin B deoxycholate as the historical standard of care following landmark clinical trial evidence demonstrating superior efficacy and survival. In a pivotal trial, voriconazole achieved a treatment success rate of 55% versus 32% for amphotericin B deoxycholate (p < .001), with significantly fewer patients requiring a switch to other licensed antifungal therapies (36% vs. 80%). Real-world observational data have further supported this profile, with voriconazole achieving treatment success in approximately 86% of patients across oral and intravenous formulations, and microbiological eradication in 76% of evaluable cases. Despite these gains, response rates across the IA treatment class have remained persistently modest — even newer agents have only elevated clinical response rates to approximately 50% in the broader invasive mould infection population, underscoring the continued unmet medical need.

More recent comparative evidence has refined the hierarchy of standard-of-care options. A network meta-analysis of 12 studies encompassing 2,428 patients and 11 antifungal agents identified isavuconazole as the monotherapy agent with the highest probability of favourable response (SUCRA 77.9%; mean rank 3.2) and the greatest reduction in all-cause mortality (SUCRA 69.1%; mean rank 4.1), followed by voriconazole and posaconazole. A 2026 literature review corroborated these findings, reporting that isavuconazole monotherapy efficacy (89.47%) significantly exceeded that of amphotericin B monotherapy (59.68%; p < 0.05), with efficacy comparable to voriconazole. For combination regimens, liposomal amphotericin B plus caspofungin demonstrated the strongest performance for both favourable response (SUCRA 84.1%) and mortality reduction (SUCRA 88.2%). Current 2025 guidelines reflect this evidence base, recommending voriconazole and isavuconazole as co-first-line agents for primary IA therapy, with posaconazole retaining its position as the preferred prophylactic agent in haematological malignancy.

The safety differentiation between agents is increasingly informing treatment selection. Amphotericin B carries the most significant toxicity burden, with strong renal toxicity signals (nephrotoxicity ROR = 24.86; renal tubular disorder ROR = 46.46) and the highest observed mortality rate among antifungal agents at 47.14% in FAERS-based analyses (2004Q1–2024Q3, n = 26,004 reports). Voriconazole is associated with hepatobiliary disorders (ROR = 4.61) and a notably elevated signal for toxic optic neuropathy (ROR = 228.80), while caspofungin carries marked hepatotoxic risk including cholestasis (ROR = 23.79). Isavuconazole and posaconazole demonstrate more favourable safety profiles — isavuconazole recorded a mortality rate of 22.70% and a life-threatening adverse event rate of only 1.89%, with a delayed median time to adverse event onset of 19.5 days compared to 6 days for caspofungin. Combination antifungal therapy, while showing mechanistic promise in preclinical models — particularly when therapy initiation is delayed — remains an area where clinical trial evidence lags substantially behind therapeutic practice in oncology and infectious disease, leaving important questions about optimal permutations unresolved.

A New Oral Option for Challenging Invasive Aspergillosis

The announcement of positive Phase III results for olorofim marks a significant moment for patients battling invasive aspergillosis, particularly those for whom existing azole therapies are no longer viable or suitable. Invasive fungal infections remain a formidable challenge, especially in the growing population of immunocompromised individuals, where they are associated with high mortality and morbidity. Current treatment paradigms often rely on agents like amphotericin B, including its lipid formulations such as AmBisome, which despite their broad efficacy, are notorious for significant adverse effects, notably nephrotoxicity and infusion-related reactions. While newer azoles like isavuconazole and posaconazole, and echinocandins, have expanded the therapeutic armamentarium, each comes with its own set of limitations, including specific toxicities and the persistent threat of resistance development.

Olorofim's success in demonstrating non-inferiority to AmBisome followed by standard of care, coupled with a distinctly favorable safety profile—especially fewer renal events—is a critical differentiator. This positions the oral antifungal as a much-needed alternative for a vulnerable patient group with limited options. The convenience of an oral formulation cannot be overstated; it promises enhanced patient compliance and could facilitate a shift towards outpatient management, reducing the burden of intravenous administration. This could lead to improved quality of life and potentially better long-term outcomes for patients who often require extended treatment durations.

However, as with any new agent, a nuanced perspective is essential. The current data, while promising, does not provide direct comparisons to all other modern antifungal agents, such as isavuconazole or posaconazole, which are also used in complex IFI cases. Furthermore, the study focused on a specific, refractory patient population, meaning its broader utility in first-line settings or against other fungal pathogens remains to be fully explored. The long-term safety profile and the potential for resistance emergence with widespread use are also important considerations that will shape its ultimate place in therapy. Nevertheless, olorofim represents a substantial step forward, offering a potentially safer and more convenient option in a disease area where innovation is desperately needed.