15 out of 18 complete responders, or 83%, demonstrated ongoing complete responses for at least 36 months without any additional treatment for RRP
5 complete responders have ongoing responses beyond 4 years
Follow-up is ongoing; median duration of complete response has not yet been reached
No new adverse safety events have been observed during long-term follow-up
US FDA granted seven-year period of orphan drug market exclusivity to PAPZIMEOS

GERMANTOWN, Md., May 30, 2026 /PRNewswire/ -- Precigen, Inc. (NASDAQ:PGEN), a commercial-stage biopharmaceutical company specializing in the advancement of innovative precision medicines to improve the lives of patients, today announced updated long-term follow-up data from the pivotal study of PAPZIMEOS™ (zopapogene imadenovec-drba) for the treatment of adults with recurrent respiratory papillomatosis (RRP). Updated durability of response data were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago in a presentation titled, "Zopapogene imadenovec-drba, a novel non-replicating adenoviral vector-based immunotherapy: Effects on complete and durable responses in recurrent respiratory papillomatosis pivotal trial."

PAPZIMEOS was granted full approval by the United States Food and Drug Administration (FDA) and was subsequently granted seven-year market exclusivity, further strengthening its position as the first and only approved therapy for the treatment of adults with RRP.

Key data highlights from the ASCO presentation include:

15 out of 18 complete responders, or 83%, demonstrated ongoing complete responses as of the April 30, 2026 data cutoff (see Figure 1);
Patients did not receive any additional treatments for RRP, including surgery or off-label investigational treatments, during this follow-up period;
All complete responders had at least 36 months of follow-up, with a median follow-up of 36 months (range: 36 to 51 months) and a mean follow-up of 40 months;
5 complete responders have ongoing responses beyond 4 years;
Median duration of complete response has not yet been reached; and
No new safety events were observed during long-term follow-up.

FIGURE 1: Ongoing Durability of Complete Response

"The presentation at ASCO marks an important maturation of the PAPZIMEOS pivotal study data, with all complete responders now followed for at least 36 months, 83% with ongoing response, including 5 patients who are surgery-free beyond 4 years," said Helen Sabzevari, PhD, President and CEO of Precigen. "For adults living with RRP, durability matters. These results continue to show that PAPZIMEOS provides sustained complete responses, reinforcing its role as the new standard of care for a disease historically managed through repeated surgeries."

About RRP

RRP is a rare, debilitating, and potentially life-threatening disease of the upper and lower respiratory tract caused by chronic HPV 6 or HPV 11 infection. RRP can lead to severe voice disturbance, compromised airways, and recurrent post-obstructive pneumonia. Although rare, RRP has the potential for transformation to malignant cancer and can be fatal. Management of RRP has primarily consisted of repeated surgeries, which do not address the underlying cause of the disease and can be associated with significant morbidity as well as significant patient and health system burden. As the number of lifetime surgeries increases, the risk for irreversible iatrogenic laryngeal injury increases with each surgery, and patients may undergo hundreds of these surgeries over their lifetimes. RRP can impact patients' work and social lives, financial stability, and mental health. Patients with RRP can experience substantial impacts to daily living with decreased quality of life and high health care utilization. Based on an internal analysis of claims data and electronic health records, there are approximately 27,000 adult RRP patients in the US.

About PAPZIMEOS^™ (zopapogene imadenovec-drba), for subcutaneous injection only

PAPZIMEOS is the first and only FDA-approved therapy for the treatment of adults with RRP and the first and only approved therapy to address the root cause of RRP. PAPZIMEOS is a non-replicating adenoviral vector-based immunotherapy designed to express a fusion antigen comprising selected regions of human papillomavirus (HPV) types 6 and 11 proteins. PAPZIMEOS is designed to generate an immune response directed against HPV 6 and HPV 11 proteins in patients with RRP. Discovered and designed in Precigen's labs using Precigen's proprietary AdenoVerse therapeutic platform, PAPZIMEOS represents a new therapeutic paradigm for RRP.

Indication and Important Safety Information

What is PAPZIMEOS?

PAPZIMEOS is a type of immunotherapy used to treat a condition called recurrent respiratory papillomatosis (RRP) in adults.

What is the most important information I should know about PAPZIMEOS?

Some people may have a reaction to the shot. Signs and symptoms may include redness, pain, swelling, itching, or warmth where the shot was given. After your first treatment, your healthcare provider will watch you for at least 30 minutes to make sure you're feeling okay.

Please contact your doctor immediately if you develop an infection, the reaction to your shot worsens, or you experience any of the below symptoms, which may indicate a systemic allergic reaction:

Difficulty breathing
Widespread rash
Facial swelling

Thrombotic events (blood clots that block your blood vessels) may occur after your PAPZIMEOS shot. Please notify your doctor immediately if you have the following symptoms:

Shortness of breath
Chest pain
Leg swelling
Persistent abdominal pain
Severe or persistent headaches
Blurred vision

What should I know before taking PAPZIMEOS?

Before taking PAPZIMEOS, tell your healthcare provider about all of your medical conditions, including:

If you are pregnant or plan to become pregnant because it is not known if PAPZIMEOS will harm the unborn baby.
If you are breastfeeding or plan to breastfeed. It is unknown if PAPZIMEOS is present in breast milk, or how it affects the breastfeeding child or milk production. Talk to your healthcare provider about the best way to feed your baby during treatment with PAPZIMEOS.

What are the most common side effects of PAPZIMEOS?

The most common side effects include:

Pain, redness, or swelling where the shot was given
Feeling tired
Chills
Fever
Muscle aches
Nausea (feeling sick)
Headache
Increased heart rate
Diarrhea
Vomiting
Sweating a lot

These are not all of the possible side effects of PAPZIMEOS. Call your healthcare provider for medical advice about side effects. You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch or call 1-800-FDA-1088. You may also report side effects to Precigen, Inc. at 1-855-PGE-NRRP (1-855-743-6777).

Please see full Prescribing Information.

Precigen: Advancing Medicine with Precision^®Precigen (NASDAQ:PGEN) is a commercial-stage biopharmaceutical company specializing in the advancement of innovative precision medicines to address difficult-to-treat diseases with high unmet patient need. Precigen is dedicated to advancing scientific breakthroughs from proof-of-concept through commercialization. With a strong commitment to innovation, Precigen is developing a robust pipeline of differentiated therapies across its core therapeutic areas of immuno-oncology, autoimmune disorders, and infectious diseases. For more information about Precigen, visit www.precigen.com or follow us on LinkedIn or YouTube.

Trademarks

Precigen, PAPZIMEOS, AdenoVerse, and Advancing Medicine with Precision are trademarks of Precigen and/or its affiliates. Other names may be trademarks of their respective owners.

Cautionary Statement Regarding Forward-Looking Statements

This press release contains "forward-looking" statements within the meaning of the safe harbor provisions of the US Private Securities Litigation Reform Act of 1995. Forward-looking statements can be identified by words such as: "anticipate," "intend," "plan," "goal," "seek," "believe," "project," "estimate," "expect," "strategy," "future," "likely," "may," "should," "will" and similar references to future periods. These statements are subject to numerous risks and uncertainties that could cause actual results to differ materially from what the Company expects. Examples of forward-looking statements include, among others, information relating to the Company's business and business plans, the success of efforts to commercialize PAPZIMEOS™ (zopapogene imadenovec-drba) for the treatment of recurrent respiratory papillomatosis (RRP) in adults including the revenue that the Company expects to realize from such efforts, the Company's ability to successfully obtain foreign regulatory approvals for PAPZIMEOS, expectations about the safety and efficacy of PAPZIMEOS, the ability of PAPZIMEOS to treat RRP, the Company's future financial and operational results including the Company's ability to reach cash flow break-even, and the Company's ability to commence clinical studies or complete ongoing clinical studies for the Company's clinical and pre-clinical stage candidates. The Company has no obligation to provide any updates to these forward-looking statements even if its expectations change. All forward-looking statements are expressly qualified in their entirety by this cautionary statement. For further information on potential risks and uncertainties, and other important factors, any of which could cause the Company's actual results to differ from those contained in the forward-looking statements, see the section entitled "Risk Factors" in the Company's most recent Annual Report on Form 10-K and subsequent reports filed with the Securities and Exchange Commission.

Investor Contact:

Steven M. Harasym

Tel: +1 (202) 365-2563

investors@precigen.com

Media Contact:

Donelle M. Gregory

press@precigen.com

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SOURCE Precigen, Inc.

Precigen Presents New Long-Term Durability Data for PAPZIMEOS, Recently Granted Seven-Year Market Exclusivity, Demonstrating Complete Responses Beyond 4 Years