Intratumoral administration of the immunologic adjuvant AS01B in combination with autologous CD1c (BDCA-1)+/CD141 (BDCA-3)+ myeloid dendritic cells plus ipilimumab and intravenous nivolumab in patients with refractory advanced melanoma

BACKGROUND

Patients with advanced melanoma who progress after treatment with immune checkpoint-inhibitors (ICI) and BRAF-/MEK-inhibitors (if BRAF V600 mutated) have no remaining effective treatment options. The presence of CD1c (BDCA-1)+ and CD141 (BDCA-3)+ myeloid dendritic cells (myDC) in the tumor microenvironment correlates with pre-existing immune recognition and responsiveness to immune checkpoint blockade. The synthetic saponin-based immune adjuvant AS01B enhances adaptive immunity through the involvement of myDC.

METHODS

In this first-in-human phase I clinical trial, patients with metastatic melanoma refractory to ICI and BRAF-/MEK inhibitors (when indicated) were recruited. Patients received an intravenous administration of low-dose nivolumab (10 mg, every 2 weeks) plus an intratumoral (IT) administration of 10 mg ipilimumab and 50 µg (0.5 mL) AS01B (every 2 weeks). All myDC, isolated from blood, were injected on day 2 into the same metastatic lesion. Tumor biopsies and blood samples were collected at baseline and repeatedly on treatment. Multiplex immunohistochemistry (mIHC) was performed on biopsy sections to characterize and quantify the IT and peritumoral immune cell composition.

RESULTS

Study treatment was feasible and well tolerated without the occurrence of unexpected adverse events in all eight patients. Four patients (50%) obtained a complete response (CR) in the injected lesions. Of these, two patients obtained an overall CR, and one patient a partial response. All responses are ongoing after more than 1 year of follow-up. One additional patient had a stable disease as best response. The disease control rate was 50%. Median progression-free survival and overall survival were 24.1 and 41.9 weeks, respectively. Baseline tumor biopsies from patients who responded to treatment had features of T-cell exclusion. During treatment, there was an increased T-cell infiltration, with a reduced mean distance between T cells and tumor cells. Peripheral blood immune cell composition did not significantly change during study treatment.

CONCLUSIONS

Combining an intratumoral injection of CD1c (BDCA-1)+ and CD141 (BDCA-3)+ myDC with repeated IT administration of ipilimumab and AS01B and systemic low-dose nivolumab is safe, feasible with promising early results, worthy of further clinical investigation.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier NCT03707808.

Current "state of the art" on dendritic cell-based cancer vaccines in melanoma

PURPOSE OF REVIEW

Dendritic cells (DCs) are the gatekeepers of our immune system and indispensable in the antitumor immune response. In recent years, their classification has been revised considerably using single-cell sequencing approaches. In this review, we focus on their unique role in cancer and how specific DC subsets can be manipulated to induce an effective and durable antitumor response.

RECENT FINDINGS

Historically, due to the ease of their isolation in sufficient cell numbers from peripheral blood, the utility of monocyte-derived DCs as therapeutic cancer vaccines was explored in the clinic. However, it became clear that naturally circulating myeloid DCs (myDC), exerting their physiological role, are a functionally more powerful cellular source of antigen presenting cells. With the advent of immunomagnetic bead technology to isolate naturally circulating DC subsets, the therapeutic value of these myDC subsets is currently being explored. Since DCs are also needed in the tumor microenvironment in order to "relicense" the activity of antitumor T cells, also intratumoral administration routes for DC vaccines are explored. In addition, to circumvent the use of expensive cellular vaccines, approaches to attract DCs to the tumor microenvironment are considered of interest in order to repair a defective cancer-immunity cycle.

SUMMARY

In recent years, the type of DCs used for vaccination and their administration route evolved considerably. Intratumoral vaccination strategies require combination with additional stimuli to ensure proper functioning of DCs in the tumor microenvironment. Moreover, intratumoral administration limits the applicability to patients with accessible lesions.

CTIM-12. A PHASE I CLINICAL TRIAL ON THE INTRACRANIAL ADMINISTRATION OF INCREASING DOSES OF IPILIMUMAB PLUS FIXED DOSE NIVOLUMAB IN PATIENTS WITH RECURRENT GLIOBLASTOMA (RGB)

BACKGROUND

Intra-operative intracerebral (iCE) administration of ipilimumab (IPI) and nivolumab (NIVO) after resection of rGB is safe and resulted in encouraging survival (NCT03233152J; Duerinck et al. JITC 2021).

METHODS

Eligible patients (pts) underwent a maximal safe resection followed by iCE administration of 5 mg IPI plus 10 mg NIVO and implantation of an Ommaya reservoir through which NIVO (10 mg) and IPI (cohort defined doses of 1-, 5- and 10 mg of IPI) were administered intracavitary (iCA) in combination with NIVO (10 mg) intravenously pre- and postoperatively and Q2w thereafter for up to 24w.

RESULTS

20 pts (13 male; median age 58y) were enrolled. One patient was excluded due to an intra-operatively diagnosed epidural bacterial infection. Respectively 4 pts were treated at the 1-, 4 pts at the 5-, and 11 pts at the 10 mg iCA IPI dose level. Median number and range of postoperative iCA administrations of IPI/NIVO was 2 (0-4) at the 1 mg dose level, 5 (1-10) at the 5 mg dose level, and pending for the 10 mg dose level. Most important treatment related adverse events were symptomatic aseptic neutrophilic pleocytosis (3 pts, all treated at the 10 mg IPI dose level), subacute cerebral edema necessitating corticosteroid treatment (5 pts), and bacterial colonization of the Ommaya reservoir (3 pts). There were no G5 AE. Nine pts have progressed and 4 pts died from progressive disease. Molecular-genetic characterization of rGB tissues, analysis of cellular and cytokine content, and NIVO/IPI concentrations in CSV samples are ongoing.

CONCLUSION

Repeated iCA administration of 10 mg NIVO plus 10 mg IPI resulted in treatment limiting aseptic neutrophilic pleocytosis. Safety of the presumed MTD of repeated 10 mg NIVO plus 5 mg IPI iCA will be further investigated.

P06.05.A Repeated intracranial administration of ipilimumab and nivolumab in patients with recurrent glioblastoma (rGB): A multi-cohort adaptive phase I clinical trial

Background

Perioperative intracerebral (iCE) administration of ipilimumab (IPI) and nivolumab (NIVO) in combination with IV NIVO was shown to be feasible, safe and associated with an encouraging survival benefit (Duerinck et al. JITC 2021). In subsequent cohorts, combination of iCE administration with biweekly intracavitary (iCA, via an Ommaya reservoir) administration of increasing doses of IPI and NIVO was investigated.

Methods

Three cohorts were defined according to resectability and postoperative treatment schedule. Patients (pts) in cohort-A and -C underwent a maximal safe resection, pts in cohort-B stereotactic biopsy only. All pts received iCE administration of 10 mg NIVO and 5 mg IPI at the end of the surgical intervention, after which an OR was implanted and an additional 10mg of NIVO and IPI (1, 5 or 10 mg) was administered iCA in cohort-C. All pts received biweekly postoperative NIVO 10 mg IV and iCA administrations of NIVO (3 dose levels were investigated in cohorts-A and -B: 1, 5, or 10 mg) for up to a maximum of 24w postoperatively. In cohort-C, 10 mg of NIVO was complemented with IPI (1, 5, or 10 mg). NGS and RNA gene expression profiling was performed on all tissue samples.

Results

In total, 44 pts were included (A: n= 16, B: n= 16, C: n= 12 recruitment ongoing). All pts in cohort-A and -B are off study treatment. All pts received the predefined dose of iCE IPI/NIVO and at least one administration of the predefined iCA dose. AE were infrequent and mostly not immune-related. Most common AE were fatigue(n=37), headache(n=25), confusion(n=18) and postoperative fever(n=15). Bacterial colonization of the Ommaya port occurred in 6 pts, subacute neurological deterioration requiring corticosteroids in 8 pts. There were no grade 5 AEs. Median PFS was 13w for cohort-A, 5w in cohort-B and 13w in cohort-C. Median OS is 43weeks in A, 29w in B and is not yet reached in cohort-C after median follow-up of 23w. OS did not differ significantly between study cohorts. OS of pts who underwent surgical resection (cohorts-A and -C) compared favorably to a historical cohort of 469 Belgian patients with rGB (treated in three prospective phase II clinical trials and a large multicenter early acces program for bevacizumab).

Conclusions

iCE followed by repeated iCA administrations of increasing doses of NIVO with/without IPI in rGB is feasible and safe without dose limiting AEs. A potential survival benefit seems restricted to pts amenable to surgical resection.

Single-domain antibody fusion proteins can target and shuttle functional proteins into macrophage mannose receptor expressing macrophages

The tumor microenvironment of numerous prevalent cancer types is abundantly infiltrated with tumor-associated macrophages (TAMs). Macrophage mannose receptor (MMR or CD206) expressing TAMs have been shown to be key promoters of tumor progression and major opponents of successful cancer therapy. Therefore, depleting MMR⁺ TAMs is an interesting approach to synergize with current antitumor therapies. We studied the potential of single-domain antibodies (sdAbs) specific for MMR to target proteins to MMR⁺ TAMs. Anti-MMR sdAbs were genetically coupled to a reporter protein, mWasabi (wasabi green, WG), generating sdAb "drug" fusion proteins (SFPs), referred to as WG-SFPs. The resulting WG-SFPs were highly efficient in targeting MMR⁺ macrophages both in vitro and in vivo. As we showed that second mitochondria-derived activator of caspase (SMAC) mimetics modulate MMR⁺ macrophages, we further coupled the anti-MMR sdAb to an active form of SMAC, referred to as tSMAC. The resulting tSMAC-SFPs were able to bind and upregulate caspase3/7 activity in MMR⁺ macrophages in vitro. In conclusion, we report the proof-of-concept of an elegant approach to conjugate anti-MMR sdAbs to proteins, which opens new avenues for targeted manipulation of MMR⁺ tumor-promoting TAMs.

The role of hepatic macrophages in liver metastasis

The liver is a major target organ for metastasis of both gastrointestinal and extra-gastrointestinal cancers. Due to its frequently inoperable nature, liver metastasis represents a leading cause of cancer-associated death worldwide. In the past years, the pivotal role of the immune system in this process is being increasingly recognised. In particular, the role of the hepatic macrophages, both recruited monocyte-derived macrophages (Mo-Mfs) and tissue-resident Kupffer cells (KCs), has been shown to be more versatile than initially imagined. However, the lack of tools to easily distinguish between these two macrophage populations has hampered the assignment of particular functionalities to specific hepatic macrophage subsets. In this Review, we highlight the most remarkable findings regarding the origin and functions of hepatic macrophage populations, and we provide a detailed description of their distinct roles in the different phases of the liver metastatic process.

Beyond the M-CSF receptor - novel therapeutic targets in tumor-associated macrophages

Tumor-associated macrophages (TAM) are by now established as important regulators of tumor progression by impacting on tumor immunity, angiogenesis, and metastasis. Hence, a multitude of approaches are currently pursued to intervene with TAM's protumor activities, the most advanced of which being a blockade of macrophage-colony stimulating factor (M-CSF)/M-CSF receptor (M-CSFR) signaling. M-CSFR signaling largely impacts on the differentiation of macrophages, including TAM, and hence strongly influences the numbers of these cells in tumors. However, a repolarization of TAM toward a more antitumor phenotype may be more elegant and may yield stronger effects on tumor growth. In this respect, several aspects of TAM behavior could be altered, such as their intratumoral localization, metabolism and regulatory pathways. Intervention strategies could include the use of small molecules but also new generations of biologicals which may complement the current success of immune checkpoint blockers. This review highlights current work on the search for new therapeutic targets in TAM.

Macrophage Metabolism As Therapeutic Target for Cancer, Atherosclerosis, and Obesity

Macrophages are not only essential components of innate immunity that contribute to host defense against infections, but also tumor growth and the maintenance of tissue homeostasis. An important feature of macrophages is their plasticity and ability to adopt diverse activation states in response to their microenvironment and in line with their functional requirements. Recent immunometabolism studies have shown that alterations in the metabolic profile of macrophages shape their activation state and function. For instance, to fulfill their respective functions lipopolysaccharides-induced pro-inflammatory macrophages and interleukin-4 activated anti-inflammatory macrophages adopt a different metabolism. Thus, metabolic reprogramming of macrophages could become a therapeutic approach to treat diseases that have a high macrophage involvement, such as cancer. In the first part of this review, we will focus on the metabolic pathways altered in differentially activated macrophages and link their metabolic aspects to their pro- and anti-inflammatory phenotype. In the second part, we will discuss how macrophage metabolism is a promising target for therapeutic intervention in inflammatory diseases and cancer.

Myeloid-derived suppressor cells as therapeutic target in hematological malignancies

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells that accumulate during pathological conditions such as cancer and are associated with a poor clinical outcome. MDSC expansion hampers the host anti-tumor immune response by inhibition of T cell proliferation, cytokine secretion, and recruitment of regulatory T cells. In addition, MDSC exert non-immunological functions including the promotion of angiogenesis, tumor invasion, and metastasis. Recent years, MDSC are considered as a potential target in solid tumors and hematological malignancies to enhance the effects of currently used immune modulating agents. This review focuses on the characteristics, distribution, functions, cell–cell interactions, and targeting of MDSC in hematological malignancies including multiple myeloma, lymphoma, and leukemia.