Pharming announces positive Phase II topline data for leniolisib in PIDs with immune dysregulation accepted as late-breaking abstract at ESID 2026

Phase II data show leniolisib improved lymphoproliferative disease markers in rare PIDs, with a safety profile consistent with prior experience.

Rhea-AI Summary

Pharming (PHAR) reported positive Phase II topline data for leniolisib in genetically identifiable primary immunodeficiencies (PIDs) with immune dysregulation linked to PI3Kδ signaling, accepted as a late-breaking abstract at ESID 2026.

The single-arm, open-label, intra-patient dose-escalation study evaluated 13 subjects and showed clinical improvements in lymphoproliferative disease, including a mean 26.4% spleen volume reduction and decreases in index lesion size. Leniolisib was generally well-tolerated, with infections as the most common events and no new safety signals, in line with its known safety profile. Additional data will be presented at the ESID meeting in October 2026 in the Netherlands.

Nine of the 13 patients also had common variable immunodeficiency (CVID), and Pharming expects to report separate Phase II topline results of leniolisib in CVID with immune dysregulation in Q4 2026 to inform potential future registrational plans.

Positive

• Mean 26.4% spleen volume reduction in lymphoproliferative disease in 13 PID patients
• Study reported no new safety signals, with tolerability consistent with known leniolisib profile
• Nine of 13 patients had CVID, supporting Q4 2026 Phase II CVID readout plans

Negative

• Phase II study was single-arm, open-label with only 13 subjects
• Safety and efficacy of leniolisib are not established for PIDs with immune dysregulation beyond APDS

News Explained

For PIDs with immune dysregulation beyond APDS, the release says leniolisib’s safety and efficacy have not been established, so these Phase II topline findings do not establish a new approved use.

Market Context

On Oct 10, 2024, the earlier Phase II initiation was accompanied by a 1.5% PHAR reaction and establi...

Analysis

On Oct 10, 2024, the earlier Phase II initiation was accompanied by a 1.5% PHAR reaction and established the same leniolisib PID program now reporting topline data, marking progression to a 26.4% mean spleen-volume reduction.

Key Figures

Study Subjects: 13 subjects Spleen Volume Reduction: 26.4% CVID Subset: 9 patients +2 more

Study Subjects

13 subjects

Phase II leniolisib trial in genetically defined PIDs

Spleen Volume Reduction

26.4%

Mean reduction in Phase II PID trial

CVID Subset

9 patients

Of 13 enrolled subjects

ESID Presentation

October 14-17, 2026

Late-breaking abstract presentation window

CVID Results Timing

Q4 2026

Expected topline Phase II results

Previous Clinical trial Reports

1 past event · Latest: Oct 10

Same Type 1 event

1. Oct 10

   Phase II trial start

   24h Move

   +1.5%

   Initiated single-arm Phase II study evaluating leniolisib in genetically defined PIDs.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

pharmacokinetic, pharmacodynamic, single-arm, open-label, +1 more

5 terms

pharmacokinetic medical

"evaluating safety and tolerability, pharmacokinetic, pharmacodynamic and efficacy measures"

Pharmacokinetic describes how a drug moves through and leaves the body — how it is absorbed, spread to tissues, broken down and excreted — like tracking a package from pickup to delivery and disposal. For investors, these properties determine effective dose, safety risks, how often a medicine must be taken, and how reliably it works, which in turn influence clinical trial success, regulatory approval chances, production complexity and a drug’s commercial value.

pharmacodynamic medical

"pharmacokinetic, pharmacodynamic and efficacy measures in 13 subjects"

Pharmacodynamic describes how a drug acts on the body — the biological effects it produces, how strong those effects are, and how long they last. For investors, pharmacodynamic data show whether a treatment actually works and at what dose, shaping expectations about a drug’s safety, effectiveness, regulatory success and market potential; think of it like testing how well a key turns a lock and whether it reliably opens the door.

single-arm technical

"This trial is a single-arm, open-label, intra-patient dose-escalation Phase II study"

A single-arm study is a clinical trial that gives all participants the same treatment and does not include a separate comparison group or placebo. Think of it like testing a new recipe by serving it to diners without offering a control dish — you can see how people respond, but you can’t directly compare results to another option. For investors, single-arm trials can speed development and reduce cost but leave more uncertainty about how a treatment stacks up against existing therapies and how regulators will view the evidence.

open-label technical

"single-arm, open-label, intra-patient dose-escalation Phase II study"

Open-label describes a situation where everyone involved in a study or process knows the full details, such as who is receiving a treatment or intervention. For investors, understanding whether a project or product is open-label helps gauge the level of transparency and potential biases, influencing trust and decision-making. It’s like knowing whether a test or experiment is conducted openly or behind closed doors.

PI3Kδ inhibitor medical

"Leniolisib is an oral small molecule phosphoinositide 3-kinase delta (PI3Kδ) inhibitor"

A PI3Kδ inhibitor is a drug that blocks the delta subtype of the phosphoinositide 3-kinase (PI3K) enzyme, a signaling protein that helps immune cells and some cancer cells grow and survive. Blocking this specific enzyme subtype can slow tumor growth or change immune activity, so investors track such drugs as a defined mechanism of action that affects likely uses, clinical trial paths, safety profiles, and commercial potential.

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• Leniolisib was generally well-tolerated, with clinical improvements across multiple measures of immune dysregulation, including reductions in lymphoproliferation
• Separately, Pharming expects to report topline results from a Phase II trial of leniolisib in CVID in Q4 2026

Leiden, the Netherlands, September 22, 2026: Pharming (Euronext Amsterdam: PHARM/Nasdaq: PHAR), a global biotechnology company focused on rare immune and genetic diseases, today announced that a late-breaking abstract highlighting positive topline data from its Phase II trial with leniolisib in genetically identifiable primary immunodeficiencies (PIDs) with immune dysregulation linked to PI3Kd signaling has been accepted at the 22^nd Biennial Meeting of the European Society for Immunodeficiencies (ESID), which will take place October 14-17, in the Netherlands.

This trial is a single-arm, open-label, intra-patient dose-escalation Phase II study of leniolisib evaluating safety and tolerability, pharmacokinetic, pharmacodynamic and efficacy measures in 13 subjects with genetically defined PIDs. The abstract will highlight leniolisib’s favorable safety and tolerability profile, as well as clinical improvements across measures of immune dysregulation. Clinical results included improvements in lymphoproliferative disease, with a mean 26.4% spleen volume reduction (SVR) and reductions in the size of index lesions. The safety observations were consistent with the known safety profile of leniolisib, with infections as the most common events observed in study subjects, and no new safety signals identified. Additional data will be presented at ESID 2026.  

Of the 13 patients enrolled in the study, nine also had a diagnosis of common variable immunodeficiency (CVID). Pharming expects to report Phase II results for leniolisib in CVID patients with immune dysregulation, with or without an identified genetic cause, in the fourth quarter of 2026.

“These results mark an important step in assessing leniolisib’s potential to address immune dysregulation in PIDs beyond APDS, potentially benefiting a substantially larger patient population,” said Anurag Relan, Chief Medical Officer of Pharming. “Given PI3Kδ’s central role in immune dysregulation mechanisms, these results are encouraging and support ongoing development of leniolisib in PID patients with APDS-like manifestations. We look forward to sharing additional results from this trial at ESID, along with topline results from our separate Phase II trial in CVID, expected in the fourth quarter, which will inform our plans for a potential registrational study in the broader CVID population.”

Abstract details:

Title: Single-arm, open-label, Phase 2 study of leniolisib in patients with inborn errors of immunity linked to dysregulated PI3K pathway signaling: Topline safety and efficacy outcomes 
Author: Gulbu Uzel, MD

The presentation will be available for viewing at ESID 2026 for the full duration of conference.

About leniolisib
Leniolisib is an oral small molecule phosphoinositide 3-kinase delta (PI3Kẟ) inhibitor approved as the first and only targeted treatment of activated phosphoinositide 3-kinase delta (PI3Kδ) syndrome (APDS) in adult and pediatric patients 12 years of age and older in the U.S., U.K., Australia, Israel, the EU, Canada, and South Korea; in children 4 to 11 years of age who weigh at least 27 kg in the U.S., and for patients 4 years of age and older in Japan.

Leniolisib inhibits the production of phosphatidylinositol-3-4-5-trisphosphate, which serves as an important cellular messenger and regulates a multitude of cell functions such as proliferation, differentiation, cytokine production, cell survival, angiogenesis, and metabolism. Results from a randomized, placebo-controlled Phase III clinical trial demonstrated statistically significant improvement in the coprimary endpoints, reflecting a favorable impact on the immune dysregulation and deficiency seen in these patients, and open label extension data has supported the safety and tolerability of long-term leniolisib administration.^1,2

Leniolisib is currently under regulatory review for the treatment of APDS in several other countries. Leniolisib is also being evaluated in two Phase II clinical trials in primary immunodeficiencies (PIDs) with immune dysregulation. The safety and efficacy of leniolisib has not been established for PIDs with immune dysregulation beyond APDS.

About Pharming
Pharming Group N.V. (Euronext Amsterdam: PHARM/Nasdaq: PHAR) is a global biotechnology company that develops and commercializes innovative medicines for people living with rare immune and genetic diseases.

We combine specialized scientific, medical, regulatory and commercial expertise to advance a focused portfolio of approved medicines and development programs that address significant unmet medical needs. Guided by insights from patients and the wider rare disease community, we are dedicated to delivering innovative therapies for some of the most challenging rare diseases.

Pharming is headquartered in Leiden, the Netherlands, with operations in the United States and Europe.

For more information, visit www.pharming.com and find us on LinkedIn.
  
Forward-looking Statements
This press release may contain forward-looking statements. Forward-looking statements are statements of future expectations that are based on management’s current expectations and assumptions and involve known and unknown risks and uncertainties that could cause actual results, performance, or events to differ materially from those expressed or implied in these statements. These forward-looking statements are identified by their use of terms and phrases such as “aim”, “ambition”, ‘‘anticipate’’, ‘‘believe’’, ‘‘could’’, ‘‘estimate’’, ‘‘expect’’, ‘‘goals’’, ‘‘intend’’, ‘‘may’’, “milestones”, ‘‘objectives’’, ‘‘outlook’’, ‘‘plan’’, ‘‘probably’’, ‘‘project’’, ‘‘risks’’, “schedule”, ‘‘seek’’, ‘‘should’’, ‘‘target’’, ‘‘will’’ and similar terms and phrases. Examples of forward-looking statements may include statements with respect to timing and progress of Pharming's preclinical studies and clinical trials of its product candidates, Pharming's clinical and commercial prospects, and Pharming's expectations regarding its projected working capital requirements and cash resources, which statements are subject to a number of risks, uncertainties and assumptions, including, but not limited to the scope, progress and expansion of Pharming's clinical trials and ramifications for the cost thereof; and clinical, scientific, regulatory, commercial, competitive and technical developments. In light of these risks and uncertainties, and other risks and uncertainties that are described in Pharming's 2025 Annual Report and the Annual Report on Form 20-F for the year ended December 31, 2025, filed with the U.S. Securities and Exchange Commission, the events and circumstances discussed in such forward-looking statements may not occur, and Pharming's actual results could differ materially and adversely from those anticipated or implied thereby. All forward-looking statements contained in this press release are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Readers should not place undue reliance on forward-looking statements. Any forward-looking statements speak only as of the date of this press release and are based on information available to Pharming as of the date of this release. Pharming does not undertake any obligation to publicly update or revise any forward-looking statement as a result of new information, future events or other information.

References 

1. Rao VK, et al. Blood. 2023;141(9):971-983.
2. Rao VK, et al. J Allergy Clin Immunol 2024;153:265-74.

For further public information, contact:
Pharming
Michael Levitan, VP Investor Relations & Capital Markets 
T: +1 (908) 705 1696 
E: investor@pharming.com 

Saskia Mehring, Head of Corporate Communications 
T: +31 6 28 32 60 41 
E: media.relations@pharming.com 

Media Relations 
Julia Deutsch (Lyra Strategic Advisory on behalf of Pharming)
E: JDeutsch@lyraadvisory.com

Netherlands: Leon Melens (LifeSpring Life Sciences Communication on behalf of Pharming) 
T: +31 6 53 81 64 27 

Attachment

• Pharming announces Phase II topline data for leniolisib in PIDs_EN_22SEP2026

FAQ

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What are the key design features of the Phase II leniolisib trial in PIDs with immune dysregulation?

The Phase II trial is described as a single-arm, open-label, intra-patient dose-escalation study. It evaluates safety and tolerability, pharmacokinetic, pharmacodynamic and efficacy measures of leniolisib in 13 subjects with genetically defined primary immunodeficiencies linked to dysregulated PI3Kδ pathway signaling.

Which clinical improvements were observed in the leniolisib Phase II PID trial?

Clinical results included improvements in lymphoproliferative disease, with a mean 26.4% spleen volume reduction (SVR) and reductions in the size of index lesions, indicating improvement across multiple measures of immune dysregulation.

How was leniolisib tolerated in this Phase II PID study?

Leniolisib was generally well-tolerated. Infections were the most common events reported in study subjects, and no new safety signals were identified. The safety observations were consistent with the known safety profile of leniolisib.

When and where will the Phase II leniolisib data be presented?

The late-breaking abstract has been accepted for the 22nd Biennial Meeting of the European Society for Immunodeficiencies (ESID), which will take place October 14–17, 2026, in the Netherlands. The presentation will be available for viewing for the full duration of the conference.

What is the title and authorship of the ESID 2026 abstract on leniolisib?

The abstract is titled “Single-arm, open-label, Phase 2 study of leniolisib in patients with inborn errors of immunity linked to dysregulated PI3K pathway signaling: Topline safety and efficacy outcomes”, and the listed author is Gulbu Uzel, MD.

What are the next steps for leniolisib development in CVID?

Nine of the 13 patients in the current study also had common variable immunodeficiency (CVID). Separately, Pharming expects to report Phase II topline results in CVID patients with immune dysregulation, with or without an identified genetic cause, in the fourth quarter of 2026, which the company said will help inform plans for a potential registrational study in the broader CVID population.

For which indications and age groups is leniolisib currently approved?

Leniolisib is an oral PI3Kδ inhibitor approved as the first targeted treatment for activated PI3Kδ syndrome (APDS) in adults and pediatric patients 12 years and older in the U.S., U.K., Australia, Israel, the EU, Canada, and South Korea; in children 4 to 11 years of age who weigh at least 27 kg in the U.S.; and in patients 4 years and older in Japan. It remains under regulatory review for APDS in several other countries.