Respira Therapeutics Enters into Agreement with Gossamer Bio (Gossamer) Granting Gossamer Option to Acquire Respira from Samsara BioCapital

- Transaction designed to accelerate development of RT234 (vardenafil Inhalation powder), an investigational first-in-class, as-needed (PRN) treatment for PAH and PH-ILD -

PALO ALTO, Calif., Sept. 25, 2025 /PRNewswire/ -- Respira Therapeutics, Inc. (Respira or the "Company"), a Samsara BioCapital portfolio company, today announced that it has entered into an agreement with Gossamer Bio, Inc. (Gossamer) (Nasdaq: GOSS) granting Gossamer an option to acquire the Company. 

Respira is developing RT234 (vardenafil inhalation powder) as the first as-needed (PRN) therapy for use in pulmonary hypertension (PH). RT234 is designed to rapidly improve PH patient function and symptoms, including for pulmonary arterial hypertension (PAH) and pulmonary hypertension associated with interstitial lung disease (PH-ILD). There are no approved PRN therapies for PAH or PH-ILD, and despite existing treatment options, the majority of PH patients continue to struggle with debilitating symptoms that disrupt daily life and limit their independence.

"We look forward to working closely with our colleagues at Gossamer, who share our commitment to people living with PH, to expeditiously develop RT234 and making this unique therapy broadly available to patients," stated John Kollins, Respira's Chief Executive Officer.

"We are excited to pair Respira's technology and expertise with Gossamer's established late-stage PH product development platform," said Michael Dybbs, member of the Respira Board of Directors and partner at Samsara BioCapital. "We are confident that this transaction favorably positions RT234 to advance into late-stage clinical development." 

Pursuant to the option agreement, Gossamer is issuing 2.5 million shares of common stock in connection with the signing.  Additionally, upon exercise of its acquisition option, Gossamer will issue an additional 1.5 million shares of common stock.  In addition, the acquisition agreement provides for certain success-based clinical, regulatory, and commercial milestone payments and a royalty on potential net sales of RT234.  During the option period, which is anticipated to continue for up to approximately two years, Gossamer will fund and Respira will undertake certain pre‑agreed development activities focused on CMC work necessary to position RT234 for successful subsequent clinical development.

Respira is being advised by Sidley Austin LLP, Boston, Massachusetts.

About Respira Therapeutics and RT234

Respira Therapeutics, Inc. is a clinical-stage biopharmaceutical company focused on developing RT234 (vardenafil inhalation powder) as the first therapy that pulmonary hypertension patients can self-administer as-needed (PRN) to provide rapid, on-demand relief of exertional symptoms, such as breathlessness and reduced ability to perform basic daily activities, on top of chronic background therapies. These symptoms are widely prevalent among PH patients and often highly debilitating and disruptive to patients' daily lives. 

RT234 incorporates novel and proprietary dry-powder formulation and inhaler technologies, including Respira's Axial Oscillating Sphere Dry Powder Inhaler (AOS™-DPI), which maximize drug delivery to the deep lung.  Vardenafil is a phosphodiesterase type 5 (PDE5) inhibitor approved in an oral dosage form for a non-PH indication.  Although the PDE5 inhibitors sildenafil and tadalafil are FDA-approved in oral dosage forms for chronic treatment of PAH, on-demand administration of PDE5 inhibitors by inhalation in PH represents a novel treatment approach. Unlike existing PH treatments, RT234 is designed to provide rapid, on-demand relief of exertional symptoms and to be used on top of background therapies.

In two completed open‑label Phase 2 studies in which a total of 56 PAH patients were treated with RT234, RT234 demonstrated rapid and clinically meaningful improvements in both hemodynamic and functional measures. Hemodynamic benefits included reductions in pulmonary vascular resistance and favorable changes in mean pulmonary arterial pressure and cardiac output. Acute functional improvements were also observed, including reduced breathlessness and increased exercise capacity during cardiopulmonary exercise testing.  To date, RT234 has demonstrated a favorable safety and tolerability profile.

About Gossamer Bio

Gossamer Bio is a late-stage, clinical biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease. Its goal is to be an industry leader in, and to enhance the lives of patients living with pulmonary hypertension.

About Samsara BioCapital

Founded in 2017, Samsara BioCapital is a leading biotech investment firm focused on identifying opportunities across public and private markets. Samsara invests across the full spectrum from early-stage start-up to late-stage clinical assets with a focus on companies that will have a significant impact on patients and address high unmet medical needs. Samsara works with entrepreneurs and top-tier management teams that they believe will have a meaningful impact on innovative therapeutics. The Samsara team has deep expertise in biotech with significant experience working together prior to founding the firm. The team is led by Srinivas Akkaraju, who has over twenty-seven years of industry experience and has an MD and a PhD in Immunology from Stanford University.

Contact:
Respira Therapeutics, Inc.
John Kollins
Chief Executive Officer
ir@respiratherapeutics.com

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SOURCE Respira Therapeutics, Inc.