Cobimetinib in Pediatric and Young Adult Patients with Relapsed or Refractory Solid Tumors (iMATRIX-cobi): A Multicenter, Phase I/II Study

Background

The MAPK pathway is an emerging target across a number of adult and pediatric tumors. Targeting the downstream effector of MAPK, MEK1, is a proposed strategy to control the growth of MAPK-dependent tumors.

Objective

iMATRIX-cobi assessed the safety, pharmacokinetics, and anti-tumor activity of cobimetinib, a highly selective MEK inhibitor, in children and young adults with relapsed/refractory solid tumors.

Patients and Methods

This multicenter Phase I/II study enrolled patients aged 6 months to < 30 years with solid tumors with known/expected MAPK pathway involvement. Patients received cobimetinib tablet or suspension formulation on Days 1–21 of a 28-day cycle. Dose escalation followed a rolling 6 design. The primary endpoint was safety; secondary endpoints were pharmacokinetics and anti-tumor activity.

Results

Of 56 enrolled patients (median age 9 years [range 3–29]), 18 received cobimetinib tablets and 38 cobimetinib suspension. Most common diagnoses were low-grade glioma (LGG; n = 32, including n = 12 in the expansion cohort) and plexiform neurofibroma within neurofibromatosis type 1 (n = 12). Six patients (11 %) experienced dose-limiting toxicities (including five ocular toxicity events), which established a pediatric recommended Phase II dose (RP2D) of 0.8 mg/kg tablet and 1.0 mg/kg suspension. Most frequently reported treatment-related adverse events were gastrointestinal and skin disorders. Steady state mean exposure (C_max, AUC_0–24) of cobimetinib at the RP2D (1.0 mg/kg suspension) was ~ 50 % lower than in adults receiving the approved 60 mg/day dose. Overall response rate was 5.4 % (3/56; all partial responses in patients with LGG).

Conclusions

The safety profile of cobimetinib in pediatrics was similar to that reported in adults. Clinical activity was observed in LGG patients with known/suspected MAPK pathway activation. Cobimetinib combination regimens may be required to improve response rates in this pediatric population.

Clinical Trial Registration

ClinicalTrials.gov NCT02639546, registered December 24, 2015.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11523-022-00888-9.

Phase I study of regorafenib in combination with vincristine and irinotecan in pediatric patients with recurrent or refractory solid tumors

10507

Background: In pediatric patients with solid tumors, regorafenib demonstrated acceptable tolerability and preliminary anti-tumor activity. This phase 1 study evaluated regorafenib in combination with vincristine/irinotecan in pediatric patients with rhabdomyosarcoma (RMS) and other solid tumors. Methods: Patients with relapsed/refractory tumors received intravenous vincristine (1.5 mg/m2, Days 1 and 8) and irinotecan (50 mg/m2/day, Days 1–5) plus once-daily oral regorafenib (patients 6– < 24 months: 60 mg/m2 escalating to 65 mg/m2; patients 2– < 18 years: 72 mg/m2 escalating to 82 mg/m2) on either Days 1–14 (concomitant dosing) or Days 8–21 (sequential dosing) during each 21-day cycle. As per protocol, at least 50% of patients were required to have RMS. Results: At the time of the cut-off, of 21 treated patients (RMS, n = 12; Ewing sarcoma, n = 5; neuroblastoma, n = 3; Wilms tumor, n = 1), two had concomitant (72 mg/m2) and 19 had sequential (72 mg/m2, n = 6; 82 mg/m2, n = 13) dosing. Median age was 10 years (1.5–17.0). Patients received a median of 3 cycles (1–17); dose reductions of irinotecan occurred in 62% of patients. Grade 3 dose-limiting toxicities were reported in both patients receiving concomitant dosing (peripheral neuropathy and liver injury; pain, vomiting, febrile aplasia) and one patient each in the sequential groups (rash and elevated AST; thrombocytopenia). Concomitant dosing was discontinued. The maximum tolerated dose and recommended phase 2 dose (RP2D) of regorafenib in the sequential combination was 82 mg/m2. The most common grade ≥3 treatment-emergent adverse events were neutropenia (71%), thrombocytopenia (33%), leukopenia (29%), anemia (24%), and ALT increased (24%). The response rate was 38%, including 1 complete (RMS) and 7 partial responders (5 RMS, 2 Ewing sarcoma); 3 of whom had prior irinotecan. Six (4 with alveolar subtype) of 12 patients with RMS had a response. Nine patients (43%) had stable disease (maximum duration 17 cycles). After the cut-off, partial response was reported for two additional patients (1 RMS, 1 Ewing sarcoma). Conclusions: Regorafenib can be combined at its single agent RP2D of 82 mg/m2 with standard-dose vincristine/irinotecan (with appropriate dose modifications) in pediatric patients with refractory/relapsed solid tumors in a sequential dosing schedule. Clinical activity was observed in patients with sarcoma. Clinical trial information: NCT02085148.

Mortality and survival rates in children and adolescents enrolled in early phase trials with a dose-finding/dose-confirmation component: An innovative therapies for children with cancer (ITCC) study

e21509

Background: Participation of children with advanced solid cancers in phase I trials raises ethical and logistic dilemmas. Life-expectancy beyond 8-12 weeks is a common inclusion criterion, but it can be difficult to gauge. This multicentric European study assessed the mortality and survival rates in pediatric phase I trials. Methods: Retrospective study of patients aged < 18 years with solid tumors enrolled in phase I trials in ITCC centres between 2015-2017. Outcome variables were described and prognostic factors analysed. Results: 256 patients across 12 centres in 5 countries were eligible. Median age 11.8 years (range, 0.5-17.9). Female:Male ratio 1:1.9. Tumor location: central nervous system (CNS) 66% vs extra-CNS 34%. Main diagnoses: 22% soft tissue sarcomas, 13% high grade gliomas, 11% osteosarcomas. Most frequent therapy: single targeted agent (63%). Ten cases (4%) were not evaluable for response and 128 (50%) had progressive disease at first evaluation. Best responses were complete in 12 cases (5%), partial in 29 (11%) and stable disease in 77 (30%). Median follow-up 7 months (range, 0.5-42.4). Median Time On Study (TOS) 2.1 months (range, 0.2-38.1). The 30 and 90-day mortality on trial were 3% (8/256) and 21% (54/256), respectively. The 90-day survival (95%CI) for patients with CNS vs extra-CNS tumors was 88% (78-93) vs 76% (68-82), respectively. One-year Overall Survival (95%CI) for the whole sample was 40% (33-46). No toxic deaths on trial were reported. Twenty-five cases (10%) survived ≥365 days on trial. Median TOS 21.5 months (range, 12.3-38.1). Compared to patients who died within 365 days from Cycle1-Day1, those on trial ≥365 days had lower rates of metastatic disease (74% vs 28%, respectively, p < 0.001), higher objective response rates (13% vs 44%, respectively, p < 0.001) and higher disease stabilization (27% vs 56%, respectively, p < 0.001). Conclusions: Currently few patients die within the first cycle of treatment. However a fifth of all patients died within 3 months from trial initiation. Patients with CNS tumors have comparable survival rates to those with extra-CNS and should not be excluded from phase I trials solely because of their diagnosis. The survival rates beyond one year remain modest.

Single-agent dose-finding cohort of a phase 1/2 study of lenvatinib (LEN) in children and adolescents with refractory or relapsed solid tumors

10544

Background: LEN is an inhibitor of vascular endothelial growth factor (VEGF) receptors 1‒3, fibroblast growth factor receptors 1‒4, platelet-derived growth factor receptor α, RET, and KIT. LEN is approved in adults for radioiodine-refractory differentiated thyroid cancer (DTC) and in combination with everolimus in patients (pts) with advanced renal cell carcinoma. We show results from the single-agent LEN dose-finding part of a phase 1/2 study in children and adolescents with solid tumors. Methods: Pts had any relapsed or refractory solid tumor, evaluable or measurable disease, were aged 2 to ≤18 years, had < 2 prior VEGF-targeted therapies, and adequate organ function. A starting dose of LEN 11 mg/m2was escalated with a time-to-event continual reassessment method. The primary endpoint was to determine the LEN recommended dose (RD). Secondary objectives included best overall response (BOR), objective response rate, safety, and pharmacokinetics (PK). Results: 23 pts enrolled (11 mg/m2: n = 5, 14 mg/m2: n = 11, 17 mg/m2: n = 7). The most common tumors were rhabdomyosarcoma (n = 5), Ewing sarcoma (n = 4), and neuroblastoma (n = 3). 3 Dose-limiting toxicities occurred in cycle 1 at 14 mg/m2 (increased alanine aminotransferase: 1; hypertension: 2). All pts had any-grade treatment-emergent adverse events (TEAEs; grade 3/4: 65%). Most common any-grade TEAEs were vomiting (52%), abdominal pain (48%), decreased appetite (48%), diarrhea (44%), and hypothyroidism (44%). 1 Pt discontinued LEN due to a LEN-related TEAE (hypertension). BOR was stable disease (n = 10). Effect of age on oral clearance and central volume of distribution was not significant. Exposure was similar to that in adults. LEN 14 mg/m2/day was therefore identified as the RD. Updated cohort 1 data will be shown. Conclusions: The LEN RD in children and adolescents was similar to the adult dose and showed a reasonable safety profile. PK in these pts did not differ significantly from that in adults. The phase 1b dose-finding study of LEN in combination with chemotherapy in osteosarcoma (OS) and phase 2 LEN monotherapy (RD 14 mg/m2) parts in DTC and OS are ongoing. Clinical trial information: NCT02432274.

Retinoid signalling and gene expression in neuroblastoma cells: RXR agonist and antagonist effects on CRABP-II and RARbeta expression

9-cis Retinoic acid (RA) induces gene expression in neuroblastoma cells more effectively and with different kinetics than other RA isomers, and could be acting in part through Retinoid X Receptors (RXRs). The aim of this study was to characterise the effects of an RXR agonist and RXR homodimer antagonist on the induction of cellular RA binding protein II (CRABP-II) and RA receptor-beta (RARbeta) in neuroblastoma cells in response to different retinoids. The RXR agonist, LDG1069, was as effective as all-trans RA in inducing gene expression, but less effective than 9-cis RA. The RXR-homodimer antagonist, LG100754, inhibited the induction of CRABP-II mRNA in SH-SY5Y neuroblastoma cells by 9-cis RA or the RXR-specific agonist LGD1069, but had no effect when used with all-trans RA. Conversely, LG100754 did not inhibit induction of RARbeta mRNA by 9-cis or all-trans RA, or by LGD1069. RAR- and RXR-specific ligands used together induced CRABP-II and RARbeta as effectively as 9-cis RA. These results demonstrate the value of combining RXR- and RAR-specific ligands to regulate RA-inducible gene expression. The possibility that RXR-homodimers mediate, in part, the induction of CRABP-II by 9-cis RA and RXR-specific ligands is discussed.

Receptor mechanisms mediating differentiation and proliferation effects of retinoids on neuroblastoma cells

The aim of this study was to clarify retinoid receptor mechanisms mediating the effects of 9-cis retinoic acid (RA) and investigate the ability of RAR- and RXR-specific analogues to induce differentiation and inhibit proliferation in neuroblastoma cells. Differentiation and the inhibition of proliferation by 9-cis RA, but not all-trans RA, were inhibited by the RXR-homodimer antagonist LG745. The RXR-specific agonist LGD1069 was ineffective at inducing differentiation or inhibiting proliferation, but showed marked synergism with RAR-specific agonists with respect to inhibiting proliferation. These data suggest that the effects of 9-cis RA are mediated via both RXR-homodimers and heterodimers. However, combinations of RAR- and RXR-selective analogues were not as effective at promoting differentiation. This study indicates that different receptor mechanisms are involved in retinoid-induced differentiation and inhibition of proliferation in neuroblastoma cells.

Retinoid-induced differentiation of neuroblastoma: comparison between LG69, an RXR-selective analogue and 9-cis retinoic acid

The aim of this study was to investigate in vitro the effects of all-trans retinoic acid (RA), 9-cis RA and the RXR-selective analogue, LG69, on the morphological differentiation, proliferation and gene expression of neuroblastoma cells. Three different cell lines were cultured with the retinoid for either 9 continuous days or for 5 days followed by 4 days without the retinoid and morphological differentiation was assessed both qualitatively and quantitatively. SH SY 5Y cell proliferation was examined by measuring cell numbers after exposure to the retinoids and RAR-beta gene expression was examined by Northern blot analysis. Morphological differentiation was more effectively induced by all-trans and 9-cis RA than by LG69. SH SY 5Y cells, when treated with 9-cis RA for only 5 of the 9 days of culture, underwent apoptosis, but this was not seen with 9 days continuous exposure nor with LG69. Inhibition of SH SY 5Y cell proliferation by all-trans or 9-cis RA was dose-dependent, but LG69 had little effect. Conversely, LG69 induced higher expression of RAR-beta than all-trans RA, but less than that produced by 9-cis RA. These data suggest that 9-cis RA as a single agent is the most effective modulator of neuroblastoma behaviour and may be the most appropriate therapeutic agent.