1. Patient has a MAPK pathway-altered solid tumor(s), including but not limited to KRAS, NRAS, HRAS, BRAF, MEK, and ERK mutations.

1. In the opinion of the treating physician, the patient has exhausted or has inadequate response to available anti-cancer treatments.

2. In the opinion of the treating physician, the patient has adequate organ function to tolerate ulixertinib as defined in section 6.1

3. Male or female patients aged ≥ 12 years.

4. Patient must be able to swallow and retain orally administered medication.

Note: Ulixertinib is primarily absorbed in the duodenum and therefore patients with any prior stomach or duodenal resection should be evaluated with that understanding.

5. For females, evidence of post-menopausal status or negative urinary or serum pregnancy test for pre-menopausal patients.

6. Highly effective contraception for both male and female patients throughout the treatment and for at least 4 months after last treatment administration. In patients under the age of 18, who are not sexually active, abstinence is an acceptable form.

7. Toxicities related to any prior treatments are either stable, stable on supportive therapy, resolved, or in the opinion of the treating physician, clinically non-significant

8. Ability to understand a written informed consent document, and the willingness to sign it. Assent will be obtained when appropriate based on the patient's age.