Isatuximab plus atezolizumab in patients with advanced solid tumors: results from a phase I/II, open-label, multicenter study

BACKGROUND

The anti-CD38 antibody isatuximab is approved for the treatment of relapsed/refractory multiple myeloma, but there are no data on its efficacy in solid tumors. This phase I/II study (NCT03637764) assessed the safety and activity of isatuximab plus atezolizumab (Isa + Atezo), an anti-programmed death-ligand 1 (PD-L1) antibody, in patients with immunotherapy-naive solid tumors: epithelial ovarian cancer (EOC), glioblastoma (GBM), hepatocellular carcinoma (HCC), and squamous cell carcinoma of the head and neck (SCCHN).

PATIENTS AND METHODS

Phase I assessed safety, tolerability, pharmacokinetics, pharmacodynamics, and the recommended phase II dose (RP2D) of isatuximab 10 mg/kg intravenously (i.v.) every week for 3 weeks followed by once every 3 weeks + atezolizumab 1200 mg i.v. every 3 weeks. Phase II used a Simon's two-stage design to assess the overall response rate or progression-free survival rate at 6 months (GBM cohort). Interim analysis was carried out at 6 months following first dose of the last enrolled patient in each cohort. Pharmacodynamic biomarkers were tested for CD38, PD-L1, tumor-infiltrating immune cells, and FOXP3+ regulatory T cells (Tregs) in the tumor microenvironment (TME).

RESULTS

Overall, 107 patients were treated (EOC, n = 18; GBM, n = 33; HCC, n = 27; SCCHN, n = 29). In phase I, Isa + Atezo showed an acceptable safety profile, no dose-limiting toxicities were observed, and RP2D was confirmed. Most patients experienced ≥1 treatment-emergent adverse event (TEAE), with ≤48.5% being grade ≥3. The most frequent TEAE was infusion reactions. The study did not continue to stage 2 based on prespecified targets. Tumor-infiltrating CD38+ immune cells were reduced and almost cleared after treatment. Isa + Atezo did not significantly modulate Tregs or PD-L1 expression in the TME.

CONCLUSIONS

Isa + Atezo had acceptable safety and tolerability. Clinical pharmacodynamic evaluation revealed efficient target engagement of isatuximab via treatment-mediated reduction of CD38+ immune cells in the TME. Based on clinical data, CD38 inhibition does not improve responsiveness to PD-L1 blockade in these patients.

A phase Ib, open-label, dose-escalation study of tivozanib and FOLFOX6 in patients (pts) with advanced gastrointestinal (GI) tumors

549

Background: Tivozanib (AV-951), a highly potent and selective tyrosine kinase inhibitor of vascular endothelial growth factor receptors (VEGFR)-1, -2, and -3, has shown additive antitumor activity with fluorouracil (5-FU) in preclinical studies. An open-label phase Ib study was conducted to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), pharmacokinetics (PK), and antitumor activity of escalating doses of tivozanib combined with standard-dose FOLFOX6 (i.e., oxaliplatin, leucovorin, and 5-FU) in pts with advanced GI tumors.

Methods: Tivozanib was administered orally once daily in 4-week cycles (3 weeks on, 1 week off), with FOLFOX6 administered on days 1 and 15 of each cycle. Pts were allowed to continue tivozanib following discontinuation of FOLFOX6.

Results: 22 pts (14 male/8 female; median age of 58 years [range, 40-75]) received 0.5 mg (n = 9), 1.0 mg (n = 3), or 1.5 mg (n = 10) tivozanib plus FOLFOX6. Pts received a median of 8.1 weeks (range, 0.1 - 43.1) of treatment. DLTs were observed in 2 pts receiving 0.5 mg tivozanib (reversible grade 3 diarrhea and grade 3 and 4 transaminase elevations, respectively) and in 2 pts receiving 1.5 mg tivozanib (reversible grade 3 seizures and grade 3 vertigo, respectively). Other grade 3/4 drug-related adverse events (AEs) included neutropenia, fatigue, and hypertension (n = 2 each); and pyrexia, pulmonary embolism, and thrombosis (n = 1 each). There was no indication that drug-related AEs in this study were more frequent or severe than those observed with tivozanib or FOLFOX6 alone. The MTD was 1.5 mg tivozanib with full dose FOLFOX6. The PK profiles of tivozanib, oxaliplatin, and 5-FU will be presented. Several durable partial responses were observed. Additional safety and efficacy data are being obtained in 8 pts currently being treated at the 1.5-mg dose level.

Conclusions: The combination of tivozanib and FOLFOX6 is tolerable and safe, with tivozanib given at its recommended dose of 1.5 mg. Observed clinical activity merits further exploration in several GI tumors, and these studies are being planned.

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Phase I, safety, pharmacokinetic and biomarker study of BAY 57–9352, an oral VEGFR-2 inhibitor, in a continuous schedule in patients with advanced solid tumors

3040

Background: BAY 57–9352 is a potent competitive inhibitor of the VEGFR-2 (IC50: 6 nM), VEGFR-3 (IC50: 4 nM), PDGFR-β and c-KIT tyrosine kinases. BAY 57–9352 showed tumor efficacy in colon, breast, pancreatic and NSCLC models. Methods: Patients with advanced solid tumors received oral BAY 57–9352 on a continuous basis, in escalating doses. One cycle was defined as 21 days of treatment. Extensive PK and PD (dynamic contrast-enhanced MRI [DCE-MRI]) evaluations were performed. Plasma biomarkers (e.g. VEGF)were also evaluated. Results: Forty patients (median 54 yrs) were enrolled at seven dose levels from 20 mg solution once daily to1500 mg twice daily (bid; 150 mg tablets) for a total of 169 cycles (range 1–17). The most frequent drug-related adverse events were nausea, hypertension, headache, vomiting, hoarseness, rash, dry skin and anorexia. One patient treated at 600 mg bid had a dose-limiting toxicity defined by an increase from grade 2 to 3 hypertension, despite the addition of an ACE-inhibitor and Ca-antagonist on day 8 of cycle 2. Another patient at that same dose level and also on day 8 cycle 2, had grade 3 AST/ALT increase, however this was not assessed as dose-limiting. Both patients continued treatment after dose reductions. Treatment was well tolerated, even at the highest dose levels. One patient with a hemangio-endothelioma (600 mg bid) had a clinical response and one desmoid tumor patient (900 mg bid) had a 53% reduction in tumor volume. BAY 57–9352 AUC increased dose proportionally up to 900 mg bid. The target AUC, based on animal models (5 mg × h/L) was reached in all patients at 900 mg bid. Dose levels exceeding 900 mg bid had similar plasma VEGF biomarker levels. Conclusions: BAY 57–9352 was well tolerated in doses up to 1500 mg bid. Based on safety, PK, PD and biomarker assessments, the recommended dose level is 900 mg bid. A 300 mg tablet is being tested for patient convenience. Combination chemotherapy studies have been started.

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VEGF, sVEGFR-2, bFGF, and IL-8 as biomarkers of the pharmacological activity of BAY 57–9352, an oral VEGFR-2 receptor tyrosine kinase inhibitor, in patients with solid tumors

3035

Background: BAY 57–9352 (BAY) is a potent anti-angiogenic drug that inhibits VEGFR-2, as well as VEGFR-1, VEGFR-3, PDGFR-β, and c-Kit tyrosine kinases. Molecular biomarkers of angiogenesis (VEGF165, soluble VEGFR-2 [sVEGFR-2], basic FGF [bFGF], and interleukin-8 [IL-8]) were used to assess the pharmacodynamic effects of BAY. Methods: Patients with advanced solid tumors from two Phase I studies received oral BAY on either an intermittent 21 day cycle (14 days on drug, 7 days off drug) or continuous schedule (21 day cycle). Doses were escalated from 20 mg once daily (od) to 1500 mg twice daily (bid). Molecular biomarkers were measured at baseline, pre-dose, and 8 hours post-dose on Days 1 and 14 of each cycle. Pharmacokinetic parameters of BAY were also assessed. Results: Plasma samples from 130 patients were analyzed for angiogenic biomarkers. Increased VEGF165 and decreased sVEGFR-2 clearly correlated with the dose of BAY, respectively. All clinical responders (as shown by tumor shrinkage) were located within the upper 10% of the total response distribution for these markers. Subgroup analysis in the three more prevalent tumors showed that patients with colorectal, renal cell, and hepatocellular carcinoma all showed biomarker responses exceeding the mean overall responses. Biomarker levels reached a plateau at daily doses of approximately 900 mg bid or 1800 mg, suggesting a saturated pharmacodynamic effect. There were no consistent changes in bFGF and IL-8. Conclusions: Both VEGF and sVEGFR-2 demonstrated a dose-dependent change with BAY 57–9352. VEGF and sVEGFR-2 may be appropriate biomarkers of the therapeutic effects of BAY, and may be useful as potential predictors of early response.

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A phase I, open-label study of the safety and pharmacokinetics (PK) of pazopanib (P) and lapatinib (L) administered concurrently

3088

Background: P is a potent tyrosine kinase inhibitor of VEGF-R1, -R2, and R3, PDGF-α/β, and c-Kit. L is a potent inhibitor of ErbB1 and ErbB2 tyrosine kinases. Several lines of evidence support combined inhibition of VEGFR and Erb in the treatment of malignancies. Methods: Patients (pts) with solid tumors received P and L daily. Safety, limited PK, biomarkers, and clinical activity were evaluated. Dose escalation occurred in cohorts of 3–6 pts based on DLT. Results: Thirty-three pts received L/P doses of 750/250 (n=4), 750/500 (n=6), 1000/250 (n=3), 1000/400 (n=2), 1000/500 (n=4), 1250/250 (n=6), 1250/400 (n=5) and 1500/200 (n=3) mg once daily (qd). Preliminary mean plasma P concentrations 24 h after administration (C24) on Day 22 were ∼19 μg/mL and 23 μg/mL after administration of 250 mg and 500 mg, respectively. These values are similar to mean C24 values observed after administration of 800 mg P alone (23.1 μg/mL). Plasma L concentrations at 750 - 1500 mg qd were similar to those observed after monotherapy. The most frequent AE’s were diarrhea (Grade (G)1 n=10, G2 n=2, G3 n=3), fatigue (G1: n=7, G2 n=5, G4 n=1), nausea (G1 n=9, G2 n=2), anorexia (G1 n=8, G2 n=3), vomiting (G1 n=9), hair depigmentation (n=7), rash (G1 n=6, G2 n=1) and abdominal cramps (G1 n=3, G2 n=2, G3 n=1). Prolonged disease stabilization of > 16 wks (median 21.5 wks) occurred in 10 pts (RCC n=3, CRC n=3, GIST n=1, mesothelioma n=1, adenocarcinoma GE junction n=1, aggressive fibromatosis n=1). 3 pts (renal cancer n=2, and giant cell tumor of the bone n=1) demonstrated tumor shrinkage of < 30% (i.e. SD by RECIST). Conclusions: Concurrent administration of pazopanib and lapatinib was generally well tolerated. Coadministration of lapatinib may alter the PK of pazopanib.

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