On September 16, 2024 iTeos Therapeutics, Inc. (Nasdaq: ITOS) ("iTeos"), a clinical-stage biopharmaceutical company pioneering the discovery and development of a new generation of immuno-oncology therapeutics for patients, reported follow-up interim data from GALAXIES Lung-201, the Phase 2 platform study sponsored by iTeos’ development partner GSK, assessing the belrestotug + dostarlimab doublet in previously untreated, unresectable, locally advanced or metastatic PD-L1 high non-small cell lung cancer (NSCLC) (Press release, iTeos Therapeutics, SEP 16, 2024, View Source [SID1234646658]).

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"We are encouraged by this interim cut of GALAXIES Lung-201 data in which a clinically meaningful, investigator-assessed Objective Response Rate was observed with belrestotug in combination with dostarlimab in first-line, PD-L1 high non-small cell lung cancer patients. Further, with roughly 60 percent confirmed ORR at three distinct doses and a meaningful difference of 30 percent compared to dostarlimab alone, we believe this underscores the potential differentiation of our TIGIT:PD-1 doublet," said Michel Detheux, Ph.D., president and chief executive officer of iTeos. "The improvement in depth of response in tumor measurement in patients treated with the doublet compared to those treated with PD-1 alone holds promising therapeutic potential for a patient population with limited options. We believe these encouraging data further support the recent initiation of GALAXIES Lung-301, the registrational Phase 3 trial assessing the TIGIT:PD-1 doublet in the same indication and setting. Based on these results, we are committed to leveraging our science to impact the lives of people living with cancer and are excited to see longer-term follow-up data in 2025."

"While checkpoint inhibitor therapies have played a significant role in how we treat non-small cell lung cancer, the medical community continues to look for new patient-centered treatment options to meaningfully improve this life-threatening condition," said Brian Henick, M.D., interim director of experimental therapeutics and director of translational research in upper-aerodigestive malignancies in medical oncology of Columbia University Irving Medical Center. "The follow-up interim analysis from the GALAXIES Lung-201 study represent promising progress and the deep responses observed in the belrestotug + dostarlimab doublet provide a strong, consistent signal.

We eagerly anticipate gaining further insights from this trial over the next year as the dataset matures."

Highlights of Interim GALAXIES Lung-201 Data

As of the June 7, 2024 data cutoff, the late-breaking interim data presented at the ESMO (Free ESMO Whitepaper) Congress were based on 124 patients eligible for safety and efficacy evaluation (modified intention-to-treat ≥5.6 months follow-up). Patients received dostarlimab or belrestotug + dostarlimab at the following dose levels: dostarlimab 500mg, belrestotug 100mg + dostarlimab 500mg (Dose A), belrestotug 400mg + dostarlimab 500mg (Dose B), and belrestotug 1000mg + dostarlimab 500mg (Dose C).

•
Clinically meaningful improvement in the primary endpoint of ORR was observed consistently across each belrestotug + dostarlimab cohort (63.3% Dose A, 65.6% Dose B and 76.7% Dose C compared to 37.5% with dostarlimab alone). cORR, defined as complete or partial response confirmed by repeat imaging ≥4 weeks after response criteria first met, was roughly 60.0% for each dose compared to 28.1% cORR for dostarlimab alone.
•
Of the patients with evaluable paired ctDNA samples (baseline and week 7), median ctDNA reduction was 65% for dostarlimab monotherapy compared to 55% for Dose A, 94% for Dose B, and 97% for Dose C.
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Belrestotug + dostarlimab led to an increase in immune-related adverse events compared to dostarlimab monotherapy, which were generally manageable. The safety profile of belrestotug in combination with dostarlimab has been broadly consistent with the known safety profile of combination therapy with checkpoint inhibitors. The most frequent treatment-related adverse events (≥15%) were skin and subcutaneous tissue disorders (50%) and endocrine disorders (26%), both commonly observed with immunotherapies.

Response measure in mITT

Dostarlimab

(N=32)

Dose A: Dostarlimab +
belrestotug

100 mg

(N=30)

Dose B: Dostarlimab +
belrestotug

400 mg

(N=32)

Dose C: Dostarimab +
belrestotug

1000 mg

(N=30)

Median follow-up, months (range)

7.0 (0.2–16.6)

8.5 (0.3–14.3)

8.5 (0.4–16.2)

6.7 (2.4–9.7)

ORR,1,2%
n (95% CI)

37.5% n=12 (21.1–56.3)

63.3%
n=19 (43.9–80.1)

65.6%
n=21 (46.8–81.4)

76.7%
n=23 (57.7–90.1)

Complete response, n (%)

0

0

0

0

Partial response, n (%)

12 (37.5%)

19 (63.3%)

21 (65.6%)

23 (76.7%)

Stable disease, n (%)

14 (43.8%)

5 (16.7%)

4 (12.5%)

5 (16.7%)

Progressive disease, n (%)

2 (6.3%)

4 (13.3%)

3 (9.4%)

2 (6.7%)

Not evaluable/no assessment,3 n (%)

4 (12.5%)

2 (6.7%)

4 (12.5%)

0

Confirmed ORR,2 %
n (95% CI)

28.1%
n=9 (13.7–46.7)

60.0%
n=18 (40.6–77.3)

59.4%
n=19 (40.6–76.3)

63.3%
n=19 (43.9–80.1)

1. unconfirmed ORR; 2. PD-L1 high (TPS ≥50%) was determined locally or centrally by DAKO 22C3 or VENTANA SP263 assay; 3. patients who only had "not evaluable" post baseline assessments, those who had a best response of "not evaluable" per RECIST 1.1 criteria, or those where no post-baseline tumor assessment was performed; CI, confidence interval

Conference Call Details

The follow-up interim data from GALAXIES Lung-201 will be discussed during a conference call and webcast presentation on Monday, September 16th, 2024 at 8:00AM ET. To register for the webcast presentation, please visit the Events section on the Investors page of the iTeos website at investors.iteostherapeutics.com. A webcast replay may be accessed on the Investors section of the iTeos website.

Phase 2 GALAXIES Lung-201 Trial Design

The Phase 2 GALAXIES Lung-201 study is a randomized, open-label, global platform study evaluating the efficacy, safety, pharmacokinetics, and pharmacodynamics of novel immunotherapy combinations compared with immunotherapy monotherapy in participants with PD-L1 high (TPS ≥50%), previously untreated, unresectable, locally advanced or metastatic NSCLC.​ Arms and interventions in this study include: pembrolizumab (anti-PD-1) monotherapy, dostarlimab (anti-PD-1) monotherapy, belrestotug (anti-TIGIT) + dostarlimab doublet combination, and belrestotug + dostarlimab + nelistotug (anti-CD96) triplet combination.

The primary endpoint of the study is investigator-assessed ORR per Response Evaluation Criteria in Solid Tumors (RECIST 1.1). Secondary endpoints include safety and additional efficacy measures such as progression free survival, overall survival, and duration of response.