Potentiating Local and Abscopal Antitumor Efficacy through Radiation with FAP-CD40 DARPin and Anti-PD1 Therapy

PURPOSE/OBJECTIVE(S)

Although the advent of Immune Checkpoint Inhibitors (ICI) has changed the facet of oncology, about 70% of patients develop resistance. CD40 is a potent costimulatory molecule that drives dendritic cells (DCs) and tumor-associated macrophages (TAMs) to prime T-cells. Clinically, agonistic CD40 antibodies have demonstrated antitumor activity, but dose-limiting toxicities have impaired efficacy. Radiation (RT), especially at higher doses, activates DCs and TAMs, but also upregulates Fibroblast Activation Protein (FAP) in the tumor microenvironment (TME). The upregulated FAP expression can be harnessed for the design of targeted drug delivery to the TME. The FAP-CD40 DARPin is a molecule that utilizes FAP and CD40 binding domains to selectively cross-link and activate CD40 in the tumor, thus avoiding systemic CD40 activation. This study aimed to evaluate if RT combined with a murine FAP-CD40 (mFAP-CD40) and ICI could improve survival and local and abscopal responses in a pre-clinical lung adenocarcinoma model. Human FAPxCD40 (MP0317) is being evaluated in Phase I trials.

MATERIALS/METHODS

The 344SQ-P tumor cells were bilaterally injected into the right and left hind legs of 129Sv/Ev mice to establish primary and secondary tumors respectively. When primary tumors reached ∼7mm in diameter, they were irradiated with 12 Gy x 3 fractions, while secondary tumors were monitored. mFAP-CD40 (5mg/kg) was injected intraperitoneally at 2, 7, and 11 days after the last fraction of RT. A backbone of α-PD1 ICI was given twice per week starting with RT for 5 shots total. Mice were euthanized when tumors reached 14mm in diameter. Lungs were collected at experimental endpoints, fixed, and enumerated for metastases.

RESULTS

For FAP detection in the TME, we first conducted an IHC analysis on 344SQ-P tumors harvested 11 days post RT. Although 5 Gy x 3 was superior to 12 Gy x 3 in upregulating FAP expression compared to unirradiated controls (P = 0.0088), we chose the 12 Gy x 3 dose for subsequent experiments due to its superiority in releasing tumor antigens, priming T-cells, and promoting abscopal responses. In our bilaterally established murine groups, we have recorded the following median survival days: Control = 23; RT = 26; RT+α-PD1 = 33; mFAP-CD40+α-PD1 = 23; and RT+mFAP-CD40+α-PD1 (Triple therapy) = 44 days. These results were further buttressed by the difference in average tumor growth observed between groups; whereby there was a significant delay in tumor growth of both primary (P<0.0001) and secondary tumors (P<0.0001) of the Triple therapy group compared to either RT+α-PD1 or mFAP-CD40+α-PD1 dual therapies. In addition, the Triple therapy cohort had a significantly lower count of lung metastases vs. control (P = 0.0007) and vs. mFAP-CD40+α-PD1 (P = 0.0246) cohorts.

CONCLUSION

mFAP-CD40 DARPin with RT and α-PD1 proved efficacious to control primary and secondary tumors in a murine lung carcinoma model with no detected toxicities.

Prothymosin α and Its C-Terminal Immunoreactive Decapeptide Show no Evidence of Acute Toxicity: A Preliminary in Silico, in Vitro and in Vivo Investigation

BACKGROUND

Members of the α-thymosin family have long been studied for their immunostimulating properties. Among them, the danger-associated molecular patterns (DAMPs) prothymosin α (proTα) and its C-terminal decapeptide proTα(100-109) have been shown to act as immunomodulators in vitro, due to their ability to promote T helper type 1 (Th1) responses. Recently, we verified these findings in vivo, showing that both proTα and proTα(100-109) enhance antitumor-reactive T cell-mediated responses.

METHODS

In view of the eventual use of proTα and proTα(100-109) in humans, we investigated their safety profile in silico, in human leukocytes and cancer cells lines in vitro, and in immunocompetent mice in vivo, in comparison to the proTα derivative thymosin alpha 1 (Τα1), a 28-mer peptide extensively studied for its safety in clinical trials.

RESULTS

In silico prediction via computational tools showed that all three peptide sequences likely are non-toxic or do not induce allergic regions. In vitro, proTα, proTα(100-109) and Tα1 did not affect the viability of human cancer cell lines and healthy donor-derived leukocytes, did not promote apoptosis or alter cell cycle distribution. Furthermore, mice injected with proTα, proTα(100-109) and Tα1 at doses equivalent to the suggested dose regimen of Tα1 in humans, did not show signs of acute toxicity, whereas proTα and proTα(100-109) increased the levels of proinflammatory and Th1-type cytokines in their peripheral blood.

CONCLUSION

Our preliminary findings suggest that proTα and proTα(100-109), even at high concentrations, are non-toxic in vitro and in an acute toxicity model in vivo; moreover, we show that the two peptides retain their immunomodulatory properties in vivo and, eventually, could be considered for therapeutic use in humans.

Abstract 1733: MP0317, a CD40xFAP targeting multi-specific DARPin® therapeutic, drives immune activation and reverts myeloid-mediated T-cell suppression in vitro and ex vivo

Therapeutic agonists targeting CD40 have shown encouraging signs of anti-tumor efficacy in patients. Despite their initial promise however, optimal dosing of systemically active agents has been limited by toxicity and their full therapeutic potential not achieved. We have previously demonstrated in vitro the ability of MP0317, a novel multi-specific DARPin® therapeutic, to selectively activate CD40 bearing B-cells, dendritic cells and macrophages in the presence of fibroblast activation protein (FAP). FAP is highly expressed in the stroma of many solid tumors and is found only at lower levels in other tissues. MP0317 utilizes FAP and CD40 binding domains to selectively cross-link and activate CD40 in the presence of FAP and thus avoid systemic CD40 activation classically associated with toxicity. Here we present new data which confirm the unique therapeutic potential of MP0317 in ex vivo model systems, demonstrate modulation of macrophage phenotype and reveal a release of T-cells from macrophage-mediated suppression. Ex vivo functional assays performed with MP0317 on dissociated human tumors demonstrated FAP-dependent activation of CD40-expressing B-cell and myeloid cell populations. Immunohistochemical analysis of tissue micro-arrays demonstrated FAP levels consistent with those required for immune cell activation in a broad range of solid tumor indications. Furthermore, by mining publicly available data, we classified tumor indications based on their immune cell content, pathway activation and MP0317 ex vivo mode of action (T cell/macrophage ratio, FAP and CD40 expression) and proposed patient populations and indications for the upcoming clinical trials. To further investigate the functional impact of MP0317, macrophages were differentiated in vitro using canonical polarising cytokines. Suppressive tumor-associated macrophage (TAM)-like cells, were repolarized by MP0317 to an anti-tumor-like phenotype. Furthermore, we explored whether modulation of macrophage phenotype by MP0317 could relieve their suppressive effect on T-cells. TAM-like macrophages potently supressed anti-CD3/28 driven T-cell activation and indeed the addition of MP0317 was found to restore T-cell response. Together these data further support MP0317's FAP targeted multimodal mechanism of action in human tumors, provide evidence for an improved therapeutic window over existing CD40 agonists and support progression to the clinic with an informed target patient profile.

Citation Format: Kyriaki Ioannou, Simone Ragusa, Joanna Roquette, Ana Florescu, Mariam Gachechiladze, Eliane Müller, Julia M. Martinez-Gomez, Sophie Barsin, Sarah Jetzer, Nicolo Rigamonti, Clara Domke, Tamara Lekishvili, Karolin Rommel, Ivana Tosevski, Anne Goubier, Philippe Legenne, Vladimir Kirkin, Mitch Levesque, Hong Ji, Rupert Kenefeck. MP0317, a CD40xFAP targeting multi-specific DARPin® therapeutic, drives immune activation and reverts myeloid-mediated T-cell suppression in vitro and ex vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1733.

Antitumor Reactive T-Cell Responses Are Enhanced In Vivo by DAMP Prothymosin Alpha and Its C-Terminal Decapeptide

Prothymosin α (proTα) and its C-terminal decapeptide proTα(100-109) were shown to pleiotropically enhance innate and adaptive immune responses. Their activities have been broadly studied in vitro, focusing primarily on the restoration of the deficient immunoreactivity of cancer patients' leukocytes. Previously, we showed that proTα and proTα(100-109) act as danger-associated molecular patterns (DAMPs), ligate Toll-like receptor-4, signal through TRIF- and MyD88-dependent pathways, promote the maturation of dendritic cells and elicit T-helper type 1 (Th1) immune responses in vitro, leading to the optimal priming of tumor antigen-reactive T-cell functions. Herein, we assessed their activity in a preclinical melanoma model. Immunocompetent mice bearing B16.F1 tumors were treated with two cycles of proTα or proTα(100-109) together with a B16.F1-derived peptide vaccine. Coadministration of proTα or proTα(100-109) and the peptide vaccine suppressed melanoma-cell proliferation, as evidenced by reduced tumor-growth rates. Higher melanoma infiltration by CD3+ T cells was observed, whereas ex vivo analysis of mouse total spleen cells verified the in vivo induction of melanoma-reactive cytotoxic responses. Additionally, increased levels of proinflammatory and Th1-type cytokines were detected in mouse serum. We propose that, in the presence of tumor antigens, DAMPs proTα and proTα(100-109) induce Th1-biased immune responses in vivo. Their adjuvant ability to orchestrate antitumor immunoreactivities can eventually be exploited therapeutically in humans.

Prothymosin Alpha: An Alarmin and More

BACKGROUND/OBJECTIVE

Prothymosin alpha (proTα) is a ubiquitous polypeptide first isolated by Haritos in 1984, whose role still remains partly elusive. We know that proTα acts both, intracellularly, as an anti-apoptotic and proliferation mediator, and extracellularly, as a biologic response modifier mediating immune responses similarly to molecules termed as "alarmins". Our research team pioneered the elucidation of the mechanisms underlying the observed activities of proTα.

RESULTS

We were the first to demonstrate that proTα levels increase during normal and abnormal cell proliferation. We showed that proTα acts pleiotropically, inducing immunomodulatory effects on immune cell populations. We revealed that the immunoreactive region of proTα is the carboxyterminal decapeptide proTα(100-109) and both molecules stimulate innate immune responses, signaling through Toll-like receptors (TLRs), specifically TLR-4. We reported that proTα and proTα(100-109) bind on the surface of human neutrophils on sites involving TLR-4, and cell activation is complemented by cytoplasmic calcium ion influx. Further, we showed that proTα and proTα(100-109) act as adjuvants upstream of lymphocyte stimulation and, in the presence of antigen, promote the expansion of antigen-reactive effectors. Most recently, we reported that proTα(100-109) may accumulate in experimentally inflamed sites and can serve as a surrogate biomarker in severe bacterial infections, proposing that extracellular release of proTα or proTα(100- 109) alerts the immune system during conditions of danger.

CONCLUSION

We, therefore, suggest that proTα, and likely proTα(100-109), act as alarmins, being important immune mediators as well as biomarkers, and could eventually become targets for new therapeutic/diagnostic approaches in immune-related diseases like cancer, inflammation, and sepsis.

New semi-synthetic analogs of oleuropein show improved anticancer activity in vitro and in vivo

Oleuropein is a glucosylated seco-iridoid present in olive fruits and leaves. Due to its broad spectrum of biological activities, including anticancer properties, oleuropein has attracted scientific attention for the past 20 years. The promising antiproliferative activity of an olive leaf extract enriched in oleuropein against a series of human cancer cell lines, prompted us to proceed with the semi-synthesis of 51 analogs of oleuropein. Following their initial screening against the estrogen receptor negative breast cancer cell line SKBR3, 7 analogs were shown to display significant cytotoxicity and were further tested against 6 additional solid tumor-derived and leukemic cell lines. The analog with the most promising antitumor activity (24) was selected for more detailed studies. 24 was non-toxic to peripheral blood mononuclear cells derived from healthy blood donors when tested at concentrations close to its half maximal inhibitory concentration. In vivo administration of 24 in melanoma-bearing mice resulted in reducing tumor size in a dose-dependent manner and in inducing anti-melanoma-reactive immune responses. Our results suggest that analog 24, emerging from the initial structure of oleuropein, represents a promising lead structure for further optimization.

The combined molecular adjuvant CASAC enhances the CD8+ T cell response to a tumor-associated self-antigen in aged, immunosenescent mice

Background

Ineffective induction of T cell mediated immunity in older individuals remains a persistent challenge for vaccine development. Thus, there is a need for more efficient and sophisticated adjuvants that will complement novel vaccine strategies for the elderly. To this end, we have investigated a previously optimized, combined molecular adjuvant, CASAC (Combined Adjuvant for Synergistic Activation of Cellular immunity), incorporating two complementary Toll-like receptor agonists, CpG and polyI:C, a class-II epitope, and interferon (IFN)-γ in aged mice.

Findings

In aged mice with typical features of immunosenescence, antigen specific CD8+ T cell responses were stimulated after serial vaccinations with CASAC or Complete/Incomplete Freund’s Adjuvant (CFA/IFA) and a class I epitope, deriving either from ovalbumin (SIINFEKL, SIL) or the melanoma-associated self-antigen, tyrosinase-related protein-2 (SVYDFFVWL, SVL). Pentamer analysis revealed that aged, CASAC/SIL-vaccinated animals had substantially higher frequencies of H-2K^b/SIL-specific CD8+ T cells compared to the CFA/IFA-vaccinated groups. Similarly, higher frequencies of H-2K^b/SVL-pentamer+ and IFN-γ+ CD8+ T cells were detected in the aged, CASAC + SVL-vaccinated mice than in their CFA/IFA-vaccinated counterparts. In both antigen settings, CASAC promoted significantly better functional CD8+ T cell activity.

Conclusion

These studies demonstrate that functional CD8+ T cells, specific for both foreign and tumour-associated self-antigens, can be effectively induced in aged immunosenescent mice using the novel multi-factorial adjuvant CASAC.

ISO-66, a novel inhibitor of macrophage migration, shows efficacy in melanoma and colon cancer models

Macrophage migration inhibitory factor (MIF) is a pleiotropic pro-inflammatory cytokine, which possesses a contributing role in cancer progression and metastasis and, thus, is now considered a promising anticancer drug target. Many MIF-inactivating strategies have proven successful in delaying cancer growth. Here, we report on the synthesis of ISO-66, a novel, highly stable, small-molecule MIF inhibitor, an analog of ISO-1 with improved characteristics. The MIF:ISO-66 co-crystal structure demonstrated that ISO-66 ligates the tautomerase active site of MIF, which has previously been shown to play an important role in its biological functions. In vitro, ISO-66 enhanced specific and non-specific anticancer immune responses, whereas prolonged administration of ISO-66 in mice with established syngeneic melanoma or colon cancer was non-toxic and resulted in a significant decrease in tumor burden. Subsequent ex vivo analysis of mouse splenocytes revealed that the observed decrease in tumor growth rates was likely mediated by the selective in vivo expansion of antitumor-reactive effector cells induced by ISO-66. Compared to other MIF-inactivating strategies employed in vivo, the anticancer activity of ISO-66 is demonstrated to be of equal or better efficacy. Our findings suggest that targeting MIF, via highly specific and stable compounds, such as ISO-66, may be effective for cancer treatment and stimulation of anticancer immune responses.

Prothymosin α and a prothymosin α-derived peptide enhance T(H)1-type immune responses against defined HER-2/neu epitopes

Background

Active cancer immunotherapies are beginning to yield clinical benefit, especially those using peptide-pulsed dendritic cells (DCs). Different adjuvants, including Toll-like receptor (TLR) agonists, commonly co-administered to cancer patients as part of a DC-based vaccine, are being widely tested in the clinical setting. However, endogenous DCs in tumor-bearing individuals are often dysfunctional, suggesting that ex vivo educated DCs might be superior inducers of anti-tumor immune responses. We have previously shown that prothymosin alpha (proTα) and its immunoreactive decapeptide proTα(100–109) induce the maturation of human DCs in vitro. The aim of this study was to investigate whether proTα- or proTα(100–109)-matured DCs are functionally competent and to provide preliminary evidence for the mode of action of these agents.

Results

Monocyte-derived DCs matured in vitro with proTα or proTα(100–109) express co-stimulatory molecules and secrete pro-inflammatory cytokines. ProTα- and proTα(100–109)-matured DCs pulsed with HER-2/neu peptides induce T_H1-type immune responses, prime autologous naïve CD8-positive (+) T cells to lyse targets expressing the HER-2/neu epitopes and to express a polyfunctional profile, and stimulate CD4+ T cell proliferation in an HER-2/neu peptide-dependent manner. DC maturation induced by proTα and proTα(100–109) is likely mediated via TLR-4, as shown by assessing TLR-4 surface expression and the levels of the intracellular adaptor molecules TIRAP, MyD88 and TRIF.

Conclusions

Our results suggest that proTα and proTα(100–109) induce both the maturation and the T cell stimulatory capacity of DCs. Although further studies are needed, evidence for a possible proTα and proTα(100–109) interaction with TLR-4 is provided. The initial hypothesis that proTα and the proTα-derived immunoactive decapeptide act as “alarmins”, provides a rationale for their eventual use as adjuvants in DC-based anti-cancer immunotherapy.

VEGF directly suppresses activation of T cells from ascites secondary to ovarian cancer via VEGF receptor type 2

Background:

Vascular endothelial growth factor action in tumour angiogenesis is well characterised; nevertheless, it functions as a key element in the promotion of the immune system’s evasion by tumours. We sought to investigate the possible direct effect of VEGF on T-cell activation and through which type of VEGF receptor it exerts this effect on cells isolated from ovarian cancer patients’ ascites.

Methods:

T cells isolated from the ascites of ovarian cancer patients were cultured with anti-CD3 and IL-2, with or without VEGF for 14 days and the number of viable T cells was counted. Cytotoxic activity of cultured T cells and expression of VEGF receptor-2 (VEGFR-2), was assayed.

Results:

The addition of VEGF in cultures significantly reduced the number and proliferation rate of T cells in a dose-dependent manner and CD3⁺ T cells expressed VEGFR-2 on their surface upon activation. Experiments with specific anti-VEGFR-2 antibodies revealed that the direct suppressive effect of VEGF on T-cell proliferation is mediated by VEGFR-2. We also showed that VEGF significantly reduced the cytotoxic activity of T cells.

Conclusion:

Our study showed that ascites-derived T cells secrete VEGF and express VEGFR-2 upon activation. Vascular endothelial growth factor directly suppresses T-cell activation via VEGFR-2.

Prothymosin alpha: a ubiquitous polypeptide with potential use in cancer diagnosis and therapy

The thymus is a central lymphoid organ with crucial role in generating T cells and maintaining homeostasis of the immune system. More than 30 peptides, initially referred to as "thymic hormones," are produced by this gland. Although the majority of them have not been proven to be thymus-specific, thymic peptides comprise an effective group of regulators, mediating important immune functions. Thymosin fraction five (TFV) was the first thymic extract shown to stimulate lymphocyte proliferation and differentiation. Subsequent fractionation of TFV led to the isolation and characterization of a series of immunoactive peptides/polypeptides, members of the thymosin family. Extensive research on prothymosin α (proTα) and thymosin α1 (Tα1) showed that they are of clinical significance and potential medical use. They may serve as molecular markers for cancer prognosis and/or as therapeutic agents for treating immunodeficiencies, autoimmune diseases and malignancies. Although the molecular mechanisms underlying their effect are yet not fully elucidated, proTα and Tα1 could be considered as candidates for cancer immunotherapy. In this review, we will focus in principle on the eventual clinical utility of proTα, both as a tumor biomarker and in triggering anticancer immune responses. Considering the experience acquired via the use of Tα1 to treat cancer patients, we will also discuss potential approaches for the future introduction of proTα into the clinical setting.

Phenoxodiol, an anticancer isoflavene, induces immunomodulatory effects in vitro and in vivo

Phenoxodiol (PXD) is a synthetic analogue of the plant isoflavone genistein with improved anticancer efficacy. Various properties and mechanisms of action have been attributed to the drug, the most important being its ability to sensitize resistant tumour cells to chemotherapy, which led to its fast track FDA approval for phase II/III clinical trials. In this study, we examined the effects of PXD on human peripheral blood mononuclear cells (PBMC) and its potential role in regulating immune responses. We show that PXD, at concentrations ≥1 μg/ml (4 μM), inhibited proliferation and reduced the viability of healthy donor-derived PBMC. In contrast, lower PXD concentrations (0.05–0.5 μg/ml) augmented, upon 3-day incubation, PBMC cytotoxicity. Experiments with purified CD56⁺ lymphocytes revealed that PXD enhanced the lytic function of natural killer (NK) cells by directly stimulating this lymphocytic subpopulation. Furthermore, in an in vivo colon cancer model, Balb/C mice administered low-dose PXD, exhibited significantly reduced tumour growth rates and prolonged survival (in 40% of the animals). Ex vivo results showed that PXD stimulated both NK and tumour-specific cell lytic activity. We conclude that PXD, when administered at low concentrations, can act as an immunomodulator, enhancing impaired immune responses, often seen in cancer-bearing individuals.

Thermodynamics of Alkoxyethanol + Alkane Mixtures

New spectroscopic data are reported for the intermolecular and intramolecular hydrogen bonding in 2-methoxyethanol +

Interaction of hand use and spatial selective attention in children

It has been argued that concurrent motor action can modulate visual spatial attention. The visual spatial biases of adult patients with unilateral neglect, for example, can be ameliorated by simultaneous use of the contralesional hand. Such improvements are most dramatic when the contralesional hand is moved within contralesional space. To date, evidence of such an interaction in neurologically healthy individuals has not been presented. Line bisection is a simple task that is sensitive to attentional spatial bias. When young children are asked to bisect horizontal lines using their right hands, they show a reliable, if small, bias that is consistent with the pattern seen in adult neglect. This bias is reversed when the left hand is used. Here, we show that these effects are significantly modulated by the location of the movements relative to the body mid-line - specifically that the conjunction of hand movements within ipsilateral space is necessary for the previously reported pattern to be observed. We further demonstrate that these effects are not present in the bisections of neurologically healthy adults. In a final study, we examined whether the hand movement effects seen in children's line bisections would persist in a purely visual task (that is when the movements were made irrelevant to the response). Again, significant modulation of children's perception by concurrent hand movements - and the relative location of those movements - was observed. The theoretical and clinical implications of the results are discussed.

Response of Charcot's arthropathy to contact casting: assessment by quantitative techniques

AIMS/HYPOTHESIS

This study used two different methods of quantitative bone scanning to study the relation between activity of Charcot's arthropathy and clinical variables over 12 months.

METHODS

Skin temperature of affected and unaffected feet was measured at baseline and every 3 months for 12 months in 17 subjects. Eight subjects underwent a three-phase quantitative bone scan at baseline and 3 monthly for 12 months. Bone isotope uptake in a standard rectangular area over the foot and tibia was analysed by the bilateral scan method (the ratio of isotope uptake of affected and unaffected feet) and the unilateral scan method (the ratio of isotope uptake of affected foot and ipsilateral tibia). The affected foot was placed in a contact cast for an average of 8 months.

RESULTS

At presentation the affected foot was hotter than the unaffected foot but the temperature became progressively cooler over 12 months. Median isotope uptake in the affected foot was 2.1% of the injected dose (interquartile range, IQR 1.9-3.0). In both scanning methods the ratio of uptake decreased after casting but at 12 months the affected foot still had more isotope uptake. There was a strong correlation between temperature difference and the ratio of uptake in the bilateral scan method (r = 0.90; p < 0.0001) but when using the unilateral scan method this relation was not significant (r = 0.1;p = 0.6). A strong relation existed between perfusion of the affected foot in the dynamic phase and isotope uptake in the delayed phase of the scans (r = 0.92; p < 0.0001).

CONCLUSION/INTERPRETATION

Bone activity and skin temperature of Charcot's arthropathy can be measured quantitatively and both improve over 12 months with contact casting. There is a strong relation between perfusion and disease activity in this condition.