The goal of this clinical trial is to learn about the safety and recommended dose of TRI-611 when administered to adults with ALK-positive non-small cell lung cancer (NSCLC). The trial will also evaluate the antitumor activity of TRI-611 in adults with ALK-positive NSCLC.

The study will be conducted in two parts. The first part will examine different doses of TRI-611. The second part will look at how well TRI-611 works on ALK-positive NSCLC when administered to three groups of participants that differ based on what type of prior therapy they have received.

In this study participants will:

• Take TRI-611 on a continued basis, provided it is well-tolerated, for as long as their disease is not progressing
• Visit the clinic approximately seven times in the first 3 months and then just once at the start of each 28-day cycle thereafter
• Keep a diary of each time they take the study medication

This is a Phase 1/2 dose escalation and dose expansion study designed to evaluate the safety and tolerability of TRI-611, identify the maximum tolerated dose (MTD) and/or the recommended phase 2 dose (RP2D), and evaluate the antitumor activity in participants with ALK-positive NSCLC.

Part 1 of the study consists of a dose escalation to determine the MTD and/or recommended dose(s) of TRI-611 for further exploration in two backfill cohorts.

Following completion of Part 1 of the study, Part 2 of the study will be initiated. The second part of the study is comprised of three cohorts (M1, M2, M3) of participants differentiated based on their previous treatment with ALK TKIs (tyrosine kinase inhibitors). During this part of the study the antitumor activity of TRI-611 will be further explored. See eligibility criteria for more details.

Inclusion Criteria:

• Pathologically confirmed diagnosis of ALK-positive non-small cell lung cancer (NSCLC)
• Measurable disease per RECIST v1.1
• Adequate bone marrow reserve and organ function
• Part 1: prior treatment with 2 to 3 ALK TKIs, prior treatment with lorlatinib is required but must not have been in the first line
• Part 2 Cohort M1: prior treatment with 2 to 3 ALK TKIs, prior treatment with lorlatinib is required but must not have been in the first line, prior treatment with neladalkib is excluded
• Part 2 Cohort M2: prior treatment with more than 3 ALK TKIs, prior treatment with lorlatinib and neladalkib is required but neither may have been in the first line
• Part 2 Cohort M3: participants without prior ALK TKI treatment

Exclusion Criteria:

• Participant's cancer has any additional driver alterations known to be a mechanism of resistance to ALK TKIs
• For participants with central nervous system (CNS) metastases or spinal cord compression, they must not be associated with progressive neurological symptoms or require increasing doses of corticosteroids to control the CNS disease
• Ongoing treatment with another anticancer treatment or investigational agent
• Known allergy/hypersensitivity to TRI-611 or any of its ingredients
• Major surgery within 4 weeks of receiving the first dose of TRI-611