Selected subjects will include males and females age ≥18 years; histologically confirmed locally advanced or metastatic solid tumors with archived tumor sample from the primary, recurrent or metastatic disease with documented MAPK pathway mutation or pathway hyperactivating mutations; advanced or recovered from all acute toxicities (≤ Grade 1) due to prior therapy; adequate renal and hepatic function; and no known history of significant cardiac or retinal disease.
Part A (Monotherapy Dose Escalation): Following screening, a total of up to 80 subjects are anticipated to establish the MTD of JSI-1187 monotherapy in subjects with locally advanced or metastatic solid tumors with MAPK pathway mutations, including hyperactivating pathway mutations or gene fusions, refractory to or relapsed on prior therapy. JSI-1187 will be administered orally at doses of 2, 4 and 8 mg twice daily, and at doses of 16, 24, 36, 56, 88 and 128 mg once or twice daily, or until an MTD for both regimens is reached, whichever is earlier, repeated every 28 days (=1 cycle). A 3+3 dose escalation schema will be followed to establish the MTD of the JSI-1187 monotherapy. Subjects will take their doses in a fasted state, 1 hour before or 2 hours after a meal. A total of 6 subjects will be treatment at the MTD before starting Part B.
(On hold, effective 05 July 2023) Part B (Combination Dose Escalation): Following screening, a total of up to 36 subjects are anticipated to establish the MTD of JSI-1187 plus dabrafenib in BRAF V600E/K-mutated unresectable or metastatic melanoma, BRAF V600E-mutated metastatic non-small cell lung cancer (NSCLC), BRAF V600E-mutated locally advanced or metastatic anaplastic thyroid cancer, or other BRAF V600E-mutated unresectable or metastatic solid tumors. A 3+3 dose escalation schema will be followed to establish the MTD of the JSI-1187 plus dabrafenib combination. Daily doses of both drugs will be taken in the fasted state. A total of 6 subjects will be treated at the JSI-1187 plus dabrafenib combined MTD before beginning Part C.
(On hold, effective 05 July 2023) Part C (Expansion Cohorts): Following screening, a total of 58 subjects in 3 cohorts are anticipated to expand the disease treatment settings of JSI-1187 in combination with dabrafenib in BRAF V600E/K-mutated melanoma or BRAF V600E-mutated NSCLC.
Cohort 1: JSI-1187 plus dabrafenib in BRAF V600E/K-mutated unresectable or metastatic melanoma after 1-3 prior therapies for metastatic disease, including anti-PD1 therapy, with or without ipilimumab, and BRAF/MEK inhibitor treatment. (n=21).
Cohort 2: JSI-1187 plus dabrafenib in BRAF V600E/K-mutated unresectable or metastatic melanoma after BRAF/MEK inhibitor adjuvant therapy for Stage 3 disease followed by 1-2 prior therapies for metastatic disease, including anti-PD-1 therapy, with or without ipilimumab, and excluding BRAF/MEK inhibitor treatment. (n=21).
Cohort 3: JSI-1187 plus dabrafenib in BRAF V600E-mutated metastatic NSCLC after 1-2 prior therapies for metastatic disease. (n=16).
JSI-1187 plus dabrafenib will be administered at the MTDs established for both drugs in Part B, repeated every 28 days (=1 cycle).
Subjects who demonstrate clinical benefit (CR, PR or SD) will be allowed to continue therapy with JSI-1187 (and dabrafenib) until progression of disease, observation of unacceptable adverse events, intercurrent illness or changes in the subject's condition that prevents further study participation.
Disease response will be assessed according to Response Evaluation Criteria in Solid Tumors (RECIST v.1.1).
Blood for hematology, coagulation parameters and serum chemistry determinations will be collected, ECGs will be taken, and ophthalmologic exams will be conducted during the study.
Blood will be collected for PK assessment of JSI-1187 and PD assessment of pRSK/RSK ratio determinations.
Tumor biopsies (optional) will be collected from consenting subjects at Screening and on-study for pRSK determination. Results will be correlated with clinical outcome.
