Lassen Therapeutics Announces Closing of Oversubscribed $85 Million Series B Financing and Announces First Patient Dosed in the Phase 1 Trial Evaluating LASN01 in Thyroid Eye Disease

Lassen Therapeutics, a clinical stage biotech company developing first-in-class antibody therapeutics, LASN01, targeting interleukin-11 receptor (IL-11R) as a potential treatment for fibro-inflammatory diseases such as TED and IPF, and a highly potent, first-in-class monoclonal antibody, LASN500, targeting the interleukin-18 binding protein (IL-18BP) as a potential treatment for cancer, today announced the closing of an oversubscribed Series B financing which raised $85 million. Frazier Life Sciences co-led the financing along with new investor Longitude Capital. The syndicate also included new investors BVF Partners and Catalio Capital Management as well as existing investors, Alta Partners and Longwood Capital. Concurrent with this financing, Brian Liu, M.D. from Longitude Capital and Matthew Hobson, Ph.D. from Catalio Capital Management have joined the Board of Directors.

Proceeds from this financing will support the LASN01 clinical program and advance IND-enabling activities for LASN500. The clinical program for LASN01 is focused primarily in TED with a cohort in IPF in the Phase 1 program. Lassen recently presented data using orbital fibroblast cells from TED patients demonstrating that LASN01 suppresses multiple markers associated with TED disease progression including hyaluronan production, cell proliferation, and other markers such as procollagen.

Recent accomplishments and future activities with use of proceeds in the LASN01 program include:

• Expansion of the Phase 1 study in IPF and TED: The Phase 1 study in healthy volunteers has been completed and demonstrated a favorable safety profile, pharmacokinetics, and target engagement, leading to expansion of the program to patient cohorts in IPF and TED; both cohorts are currently enrolling patients with the first patient dosed in TED.
• Initiation and expansion of the Phase 2 program in TED in the US and ex-US: Lassen has received US IND clearance from the FDA as well as Clinical Trial Authorisation (CTA) from the Medicine and Healthcare Products Regulatory Agency (MHRA). One site is active with additional sites being activated in the US and ex-US.
• Development of subcutaneous formulation: Process development work to create a subcutaneous presentation of LASN01 has been initiated.

"I am very pleased with the recent advancements at Lassen, particularly in successfully concluding the Series B financing round which will facilitate the continued development of our two pipeline products," said Maria Fardis, Ph.D., Chief Executive Officer of Lassen. "The proceeds allow us to advance LASN01 Phase 1 and 2 clinical programs and develop a subcutaneous formulation for LASN01. This antibody has significant potential as a treatment for fibro-inflammatory disorders including TED. Our data in orbital fibroblasts have been highly encouraging and paired with our Phase 1 single and multiple ascending dose safety data, support advancement of LASN01 in Phase 2 for TED."

"We are very excited about Lassen and the opportunity to develop two first-in-class programs, one in fibro-inflammatory disorders and the other in cancer, along with the management team's ability to expeditiously execute these programs in pursuit of new therapeutic options for patients," said Brian Liu, M.D. Managing Director at Longitude Capital. "We are encouraged by the progress of LASN01, the lead program at Lassen which is entering Phase 2 and is a first-in-class antibody that binds to a novel target, an important differentiator in a broad set of fibro-inflammatory indications addressing serious unmet medical needs."

About LASN01

LASN01 is a first-in-class monoclonal antibody targeting the receptor for IL-11 (IL-11R). IL-11 is a central mediator of fibro-inflammatory disorders and blocking its activity has the potential to offer a novel modality for treatment of thyroid eye disease (TED) and other fibro-inflammatory diseases. In preclinical studies, LASN01 led to the suppression of cell proliferation, hyaluronan secretion, and procollagen from primary TED orbital fibroblasts. These results indicate that LASN01 has the potential to be a new therapeutic agent for the treatment of TED. Please refer to www.clincialtrials.gov (NCT 05331300) for additional details related to this clinical trial.

About LASN500

LASN500 is a highly potent, first-in-class monoclonal antibody targeting the IL-18 binding protein (IL-18BP). IL-18BP is elevated at the tumor site in multiple cancer indications and blockade of this protein allows for elevation of IL-18 at the tumor site, which is expected to provide a better safety profile.

About Lassen Therapeutics

Lassen Therapeutics is a clinical-stage biotech company developing first-in-class antibodies as potential treatments for fibro-inflammatory disorders, such as thyroid eye disease (TED), and cancer. The company's lead candidate, LASN01, is a first-in-class monoclonal antibody targeting IL-11 receptor (IL-11R) and is currently being evaluated for the treatment of TED and idiopathic pulmonary fibrosis (IPF). Lassen is also developing LASN500, a highly potent, first-in-class monoclonal antibody targeting the IL-18 binding protein (IL-18BP) for cancer.

For more information, please visit www.lassentherapeutics.com and follow us on LinkedIn.

About Frazier Life Sciences

Frazier Life Sciences invests globally in private and publicly-traded companies that discover, develop and commercialize innovative biopharmaceuticals. Frazier Life Sciences' funds comprise over $3.3 billion in capital raised, including venture funds focusing on company creation and private companies, and public funds focused on small and mid-cap public companies. Since 2005, over 60 Frazier Life Sciences portfolio companies, many of which were created or seeded by Frazier, have completed IPOs or M&As. The Frazier Life Sciences team consists of over 40 professionals with deep experience in biopharmaceuticals, primarily located in Palo Alto, CA (headquarters), San Diego, Seattle, Boston, New York, and London.

About Longitude Capital

Longitude Capital is a leading healthcare venture capital firm that invests in transformative biotechnology, medical technology, and health solutions companies seeking to improve clinical outcomes, enhance patient quality of life, and drive efficiency of healthcare delivery. Founded in 2006, Longitude Capital invests in both privately held and publicly traded companies through a variety of investment approaches. Longitude Capital has offices in Menlo Park, CA, Greenwich, CT, and Boston. For more information, please visit www.longitudecapital.com or LinkedIn.