Gossamer Bio, Inc. Q4 FY2021 earnings call

• 2021 was a year of execution for Gossamer, with 2 upcoming proof-of-concept Phase II readouts in ulcerative colitis (GB004) and Pulmonary Arterial Hypertension (seralutinib) in 2022.
• GB004's SHIFT-UC study is on track for week 12 primary endpoint top line results in Q2 2022 and week 36 treat-through endpoints in Q4 2022; no impact on 12-week data from Ukraine/Russia, but monitoring 36-week data.
• Seralutinib's TORREY study is enrolling patients, expects top line data in H2 2022; high percentage of patients continuing to open-label extension.
• GB5121, a CNS-penetrant BTK inhibitor, to enter global Phase Ib/II clinical study in PCNSL in H1 2022; IND application submitted to FDA.

For the quarter ended December 31, 2021, R&D expenses were $41 million compared to $39 million for the same period in 2020. R&D expenses for the full year 2021 were $170 million compared to $161 million for 2020. G&A expenses in the fourth quarter were $11 million compared to $16 million for the same period in 2020. G&A expenses for the full year 2021 were $46 million compared to $50 million for the full year of 2020. The company ended the year with $325 million of cash and cash equivalents.

• Expect to read out top line data from the TORREY study in the second half of 2021, barring further COVID-19 impacts.
• GB5121 to enter a global Phase Ib/II clinical study in PCNSL in the first half of 2022.

• The ongoing COVID-19 pandemic may adversely affect the ability to meet guidance related to timely initiation and completion of clinical studies, and release of trial results.

Q: On the UC side, how to extrapolate early histologic benefits to remission?

A: Chief Medical Officer Richard Aranda explains it's challenging but recent literature shows early histologic changes may reflect later clinical endpoints.

Q: On the TORREY study, percentage of patients rolling over to open-label?

A: Faheem Hasnain and Richard Aranda mention high retention rate similar to the PULSAR study of sotatercept.

Q: On GB5121, details on dose range in healthy volunteer study?

A: Chief Medical Officer Richard Aranda explains using BTK receptor occupancy to guide dosing, starting at a dose for mid-range receptor occupancy and escalating to assess safety.