Intratumoral delivery of tavokinogene telseplasmid yields systemic immune responses in metastatic melanoma patients

BACKGROUND

Interleukin 12 (IL-12) is a pivotal regulator of innate and adaptive immunity. We conducted a prospective open-label, phase II clinical trial of electroporated plasmid IL-12 in advanced melanoma patients (NCT01502293).

PATIENTS AND METHODS

Patients with stage III/IV melanoma were treated intratumorally with plasmid encoding IL-12 (tavokinogene telseplasmid; tavo), 0.5 mg/ml followed by electroporation (six pulses, 1500 V/cm) on days 1, 5, and 8 every 90 days in the main study and additional patients were treated in two alternative schedule exploration cohorts. Correlative analyses for programmed death-ligand 1 (PD-L1), flow cytometry to assess changes in immune cell subsets, and analysis of immune-related gene expression were carried out on pre- and post-treatment samples from study patients, as well as from additional patients treated during exploration of additional dosing schedules beyond the pre-specified protocol dosing schedule. Response was measured by study-specific criteria to maximize detection of latent and potentially transient immune responses in patients with multiple skin lesions and toxicities were graded by the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0).

RESULTS

The objective overall response rate was 35.7% in the main study (29.8% in all cohorts), with a complete response rate of 17.9% (10.6% in all cohorts). The median progression-free survival in the main study was 3.7 months while the median overall survival was not reached at a median follow up of 29.7 months. A total of 46% of patients in all cohorts with uninjected lesions experienced regression of at least one of these lesions and 25% had a net regression of all untreated lesions. Transcriptomic and immunohistochemistry analysis showed that immune activation and co-stimulatory transcripts were up-regulated but there was also increased adaptive immune resistance.

CONCLUSIONS

Intratumoral Tavo was well tolerated and led to systemic immune responses in advanced melanoma patients. While tumor regression and increased immune infiltration were observed in treated as well as untreated/distal lesions, adaptive immune resistance limited the response.

Abstract P2-09-11: Intratumoral tavokinogene telseplasmid and electroporation in pre-treated inoperable locally advanced or recurrent triple-negative breast cancer

Introduction: Triple negative breast cancer (TNBC) accounts for approximately 15% of breast cancer diagnoses and is associated with a higher risk of recurrence and more aggressive course in the metastatic setting. Emerging data suggest that some patients with TNBC benefit from immune-based therapies targeting the anti-programmed cell death protein 1 (PD-1)/PD-1 ligand 1 (PD-L1) axis, but success has been limited in poorly immunogenic tumors. Thus, combination therapies that drive an influx of CD8+ tumor infiltrating lymphocytes (TILs) and/or upregulate PD-L1 expression are required to increase response rates to these therapeutics. Intratumoral injection of plasmid IL-12 (tavokinogene telseplasmid; tavo) followed by electroporation (IT-tavo-EP) is a gene therapy approach that drives local expression of the proinflammatory cytokine, interleukin-12 (IL-12). Local expression of IL-12 is hypothesized to result in increased TILs and enhanced expression of proinflammatory cytokines, resulting in conversion of poorly-immunogenic/low TIL TNBC tumors into highly inflamed immunologically active lesions while demonstrating a high safety profile.

Methods: OMS-I140 is a phase I, non-randomized, open-label study of IT-tavo-EP in patients with inoperable locally advanced, metastatic and/or treatment-refractory TNBC (NCT02531425). Eligible patients have pre-treated TNBC and at least 2 anatomically distinct cutaneous or subcutaneous lesions accessible for injection and electroporation, with or without other regional or distant metastases. 10 patients are planned for enrollment. IT-tavo-EP is administered on Days 1, 5 and 8 of a single 28-day cycle. Tavo is injected intratumorally (based on tumor volume) at a concentration of 0.5 mg/mL and immediately followed by co-localized electroporation (6 pulses at 1500 V/cm with 1-second intervals). Tumor biopsies are obtained at baseline and post-treatment on day 28 of both treated and untreated lesions to determine if this therapy can promote a pro-inflammatory molecular and histologic signature. Pain scores and adverse events are recorded.

Results: To date, nine patients have completed study therapy. Reported treatment-related adverse events include pain associated with electroporation (grade 1) in 8 patients and fatigue (grade 1) in 1 patient. Median pain score (range 0-10) immediately after treatment was 2 (range 0-10) and 5 minutes post-treatment was 0 (range 0-6). In some patients, treatment-related increases in CD8+ TIL density have been observed by intratumoral chromogenic staining. Further immune profiling is being conducted to characterize the tumor microenvironment pre- and post-therapy. A subset of patients with treatment refractory TNBC received anti-PD-1 monotherapy as their immediate next therapy with clinical response observed. Updated data will be presented.

Conclusions: Our data suggest that IT-tavo-EP is a safe and tolerable TIL stimulating therapy in TNBC. Further study of IT-tavo-EP in combination with pembrolizumab in pretreated metastatic TNBC is planned.

Citation Format: Telli ML, Zablotsky K, Le MH, Canton D, Browning E, Bannavong D, Gargosky S, Wapnir I. Intratumoral tavokinogene telseplasmid and electroporation in pre-treated inoperable locally advanced or recurrent triple-negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-11.

The role of growth hormone in adaptation to massive small intestinal resection in rats

The residual small bowel undergoes profound adaptive alterations after surgical resection. GH is considered to have a role in regulation of these adaptive changes, but its precise role is unknown. We investigated the role of GH by studying the response to intestinal resection in rats with isolated GH deficiency. Spontaneous dwarf rats, a strain of rats with congenital isolated GH deficiency, underwent 60% resection of the small intestine and parameters of the response of the intestinal remnant were compared with age-matched GH-deficient rats undergoing transection, GH-normal rats undergoing 60% resection, and nonmanipulated GH-normal rats. Deficiency of GH did not inhibit hyperplasia of the mucosal mass of the intestinal remnant, indicating that GH is not required for regulation of this aspect of the adaptive response. However, GH deficiency resulted in lack of accumulation of mucosal protein, including lack of accumulation of digestive hydrolases. In addition, GH deficiency resulted in alterations in processing of digestive hydrolases of the distal intestine, indicating that GH may have region-specific effects on small intestinal function. We conclude that GH is required for the normal expression of specific components of the adaptive response to massive small intestinal resection, but not for all aspects. The aspects that require GH appear to involve protein synthesis and processing.

Hormonal and metabolic effects and pharmacokinetics of recombinant insulin-like growth factor-I in growth hormone receptor deficiency/Laron syndrome

Profound growth failure despite elevated GH levels in GH receptor deficiency (GHRD) results from reduced insulin-like growth factor-I (IGF-I) synthesis. Recent reports of improved growth velocity in children with GHRD during IGF-I therapy indicate growth-promoting potential in humans. We evaluated the pharmacokinetics and metabolic/hormonal effects of recombinant human IGF-I (40 micrograms/kg every 12 h) given sc for 7 days to six adults with GHRD. Hypoglycemia (< 2.5 mmol/L) did not occur, and mean 2 h postprandial insulin levels were reduced. Urinary calcium increased 2-fold (P < 0.01), and serum calcium was unchanged. The mean integrated 24-h GH level was suppressed (6.5 +/- 2.1 to 1 +/- 0.2 micrograms/L), as were the number of peaks, area under the curve, and clonidine-stimulated GH release (all P < 0.05). The mean pretreatment IGF-I level (36 +/- 2 micrograms/L) was 19% of the Ecuadorian control value (190 +/- 15 micrograms/L), it achieved a peak (253 +/- 11 micrograms/L) between 2-6 h after IGF-I injection, and at 12 h it was 137 +/- 8 micrograms/L. There were no significant changes in the half-life (8.2 +/- 1.5 to 9.7 +/- 1.9 h) or metabolic clearance (0.35 +/- 0.1 to 0.24 +/- 0.05 mL/kg.min) between days 1 and 7; however, distribution volume increased (183 +/- 10 to 266 +/- 36 mL/kg; P < 0.03). Baseline IGF-II levels were 47% of the control value and decreased during IGF-I therapy (273 +/- 10 to 178 +/- 9 micrograms/L; P < 0.01), correlating inversely with IGF-I levels (r = -0.3; P < 0.001). Although IGF-binding protein-3 (IGFBP-3) levels were not significantly influenced, baseline IGFBP-2 levels (153% of the control) increased 45% (P < 0.01). We conclude that IGF-I (40 micrograms/kg every 12 h) given sc to adults with GHRD is safe; achieves normal levels of IGF-I; reduces insulin, IGF-II, and GH levels; and increases IGFBP-2 concentrations and urinary excretion of calcium.