Potent GCN2 Inhibitor Capable of Reversing MDSC-Driven T Cell Suppression Demonstrates In Vivo Efficacy as a Single Agent and in Combination with Anti-Angiogenesis Therapy

General control nonderepressible 2 (GCN2) protein kinase is a cellular stress sensor within the tumor microenvironment (TME), whose signaling cascade has been proposed to contribute to immune escape in tumors. Herein, we report the discovery of cell-potent GCN2 inhibitors with excellent selectivity against its closely related Integrated Stress Response (ISR) family members heme-regulated inhibitor kinase (HRI), protein kinase R (PKR), and (PKR)-like endoplasmic reticulum kinase (PERK), as well as good kinome-wide selectivity and favorable PK. In mice, compound 39 engages GCN2 at levels ≥80% with an oral dose of 15 mg/kg BID. We also demonstrate the ability of compound 39 to alleviate MDSC-related T cell suppression and restore T cell proliferation, similar to the effect seen in MDSCs from GCN2 knockout mice. In the LL2 syngeneic mouse model, compound 39 demonstrates significant tumor growth inhibition (TGI) as a single agent. Furthermore, TGI mediated by anti-VEGFR was enhanced by treatment with compound 39 demonstrating the complementarity of these two mechanisms.

Novel Piperidinyl-Azetidines as Potent and Selective CCR4 Antagonists Elicit Antitumor Response as a Single Agent and in Combination with Checkpoint Inhibitors

The C-C chemokine receptor 4 (CCR4) is broadly expressed on regulatory T cells (T_reg) as well as other circulating and tissue-resident T cells. T_reg can be recruited to the tumor microenvironment (TME) through the C-C chemokines CCL17 and CCL22. T_reg accumulation in the TME has been shown to dampen the antitumor immune response and is thought to be an important driver in tumor immune evasion. Preclinical and clinical data suggest that reducing the T_reg population in the TME can potentiate the antitumor immune response of checkpoint inhibitors. We have developed small-molecule antagonists of CCR4, featuring a novel piperidinyl-azetidine motif, that inhibit the recruitment of T_reg into the TME and elicit antitumor responses as a single agent or in combination with an immune checkpoint blockade. The discovery of these potent, selective, and orally bioavailable CCR4 antagonists, and their activity in in vitro and in vivo models, is described herein.

Abstract 4600: Potent and selective C-C chemokine receptor (CCR4) antagonists potentiate anti-tumor immune responses by inhibiting regulatory T cells (Treg)

Naturally suppressive CD4+ Foxp3+ Treg are essential for immune tolerance. Although Treg-mediated suppression of effector cells is important to control inflammation and prevent autoimmune diseases, the presence of Treg in the tumor microenvironment (TME) has been shown to dampen anti-tumor immune responses. Human Treg express CCR4, the receptor for the chemokines CCL17 and CCL22. These chemokines are produced by tumor cells, tumor-associated macrophages and dendritic cells, as well as by effector T cells (Teff). Preclinical and clinical data supports a role for CCR4-mediated recruitment and accumulation of Treg in the TME which can be associated with poor prognosis. Further, recent longitudinal studies in patients receiving IO agents demonstrate an influx of Treg in responding patients which may dampen optimal anti-tumor responses. Therefore, CCR4 is an ideal target to selectively block Treg recruitment into the TME.

We have developed structurally unique series of small molecule antagonists of CCR4. These antagonists have cellular potencies in multiple assays (e.g. chemotaxis of primary human Treg in 100% serum) in the low double-digit nM range. Representative compounds are selective against other chemokine receptors, GPCRs and ion channels, including the hERG channel, and lack inhibition of common human CYP450 enzymes. Moreover, compounds have excellent in vitro and in vivo ADME properties, consistent with convenient oral dosing. In preclinical syngeneic tumor models, these CCR4 antagonists block Treg migration and support expansion of activated Teff. In contrast to the non-selective approach of depleting anti-CCR4 antibodies, our compounds reduce Treg in the tumor, but not in peripheral tissues such as blood, spleen or skin. In preclinical efficacy studies, CCR4 antagonists potentiate the anti-tumor effects of various checkpoint inhibitors and immune stimulators such as anti-PD-L1 and anti-CD137 antibodies. We observe enhanced tumor growth inhibition and increased tumor regressions when these agents are combined with CCR4 antagonists, without any gross toxicity. Further characterization of these CCR4 antagonists and their anti-tumor effects will be described.

Citation Format: Oezcan Talay, Lisa Marshall, Cesar Meleza, Maureen K. Reilly, Omar Robles, Mikhail Zibisky, Abood Okal, Lisa Seitz, Jenny McKinnell, Scott Jacobson, Erin Riegler, Emily Karbaz, David Chian, Angela Wadsworth, Paul Kassner, David Wustrow, Jordan S. Fridman. Potent and selective C-C chemokine receptor (CCR4) antagonists potentiate anti-tumor immune responses by inhibiting regulatory T cells (Treg) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4600. doi:10.1158/1538-7445.AM2017-4600

Abstract 4290: Potent and selective next generation inhibitors of indoleamine-2,3-dioxygenase (IDO1) for the treatment of cancer

The IDO1 pathway has been proposed to mediate immunosuppressive effects in the tumor microenvironment through its role in the catabolism of tryptophan, resulting in effects on the differentiation and proliferation of T cells. IDO1 inhibition has shown promising clinical benefit as well as exacerbated toxicity in the treatment of melanoma, when combined with the anti-CTLA-4 antibody ipilimumab.

We have discovered a novel class of highly selective small molecule inhibitors of IDO1 which surpass the potency of the compounds currently in clinical development. These compounds potently inhibit IDO1 activity in IFN-γ stimulated HeLa cells with single digit nM potency. Importantly, they also retain their potency in the presence of human serum, with IC50 values ranging between 5 and 15 nM in this more physiologically relevant media. Consistent with the role of IDO1+ dendritic cells in the suppression of T cell proliferation, this series of molecules is capable of restoring the proliferative capacity of human T cells (which is inhibited by allogeneic IDO1+ dendritic cells) with EC50 values of 2-3 nM. The molecules exhibit preclinical PK characteristics that are suitable for assessing the contribution of IDO1 to tumor growth in murine models, both alone and in combination with other therapeutic agents. The compounds have high metabolic stability against cultured human hepatocytes and exhibit preclinical PK and ADME characteristics consistent with once-daily dosing in humans. The full preclinical profile of one of these molecules, selected for clinical evaluation, will be the focus of this presentation.

In conclusion, we have discovered a novel class of small molecule inhibitors of IDO1, which provides a preclinical basis for the clinical evaluation of a next generation IDO1 inhibitor in combination with other therapeutic agents.

Citation Format: Jay P. Powers, Matthew J. Walters, Rajkumar Noubade, Stephen W. Young, Lisa Marshall, Jan Melom, Adam Park, Nick Shah, Pia Bjork, Jordan S. Fridman, Hilary P. Beck, David Chian, Jenny V. McKinnell, Maksim Osipov, Maureen K. Reilly, Hunter P. Shunatona, James R. Walker, Mikhail Zibinsky, Juan C. Jaen. Potent and selective next generation inhibitors of indoleamine-2,3-dioxygenase (IDO1) for the treatment of cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4290. doi:10.1158/1538-7445.AM2015-4290

DABO Boronates: Stable Heterocyclic Boronic Acid Complexes for Use in Suzuki-Miyaura Cross-Coupling Reactions

Diethanolamine complexed heterocyclic boronic acids (DABO boronates) are air-stable reagents that can be used directly in Suzuki-Miyaura reactions in the presence of water or a protic co-solvent. Interestingly, heterocyclic DABO boronates can be stored for extended periods of time at room temperature with no noticeable degradation, unlike their boronic acid counterparts. Heterocyclic DABO boronates constitute an operationally simple and efficient alternative to other boronic acid derivatives as coupling partners in palladium catalyzed cross-coupling reactions under standard Suzuki-Miyaura conditions.

Allyl transfer to aldehydes and ketones by Brønsted acid activation of allyl and crotyl 1,3,2-dioxazaborolidines

Alkyl dioxazaborolidines are air-stable and often crystalline organoboranes. A variety of Brønsted acids activate allyl dioxazaborolidines to generate reactive allyl-transfer reagents in situ. These reagents add to aldehydes and ketones to generate the corresponding alcohols in good yields under mild conditions. The E- and Z-crotyl reagents react diastereoselectively with aldehydes and ketones to produce anti and syn adducts, respectively, a result consistent with a cyclic transition state (type I mechanism).

Analysis of blunt and penetrating injury of the innominate and subclavian arteries

Injury to the innominate or subclavian artery is an uncommon but difficult management problem. Review of trauma admissions from August 1983 to August 1992 revealed 21 patients who sustained injury to the innominate or subclavian artery. Eight patients sustained blunt trauma, while 13 patients sustained penetrating injuries. The mechanism of injury was variable, and associated injuries were common in both blunt and penetrating trauma. Injuries involved the right innominate or subclavian artery in 10 patients and the left subclavian artery in 11 patients. Twenty patients were managed operatively. Primary repair was preferred for penetrating injuries, whereas a bypass graft was more common for blunt injuries (P = 0.41). Patients with penetrating injury were more unstable at presentation (admission systolic blood pressure 73 mm Hg vs 119 mm Hg, P = 0.006; preoperative evaluation time 66 min vs 319 min, P = 0.002) and required more blood transfusions (5 units vs 26 units, P = 0.007) than patients with blunt injuries. Mortality for the entire series was 24 per cent (0% blunt vs 38% penetrating, P = 0.047). Hospital days (28 vs 48) and ICU days (8 vs 14) were longer for survivors of penetrating injuries (P = NS). Complications were common in both groups. Innominate/subclavian artery injury remains a significant cause of mortality and morbidity.

Carotid artery replacement in conjunction with resection of squamous cell carcinoma of the neck: preliminary results

Squamous cell carcinoma can invade the carotid artery. The treatment options then include irradiation, "palliative peeling" of tumor from the artery, and carotid resection with ligation or in-line grafting. Twelve patients with invasion of the carotid artery by cancer had en bloc resection of the artery and tumor. Reconstruction after in-line carotid artery grafting with autogenous vein was completed with a myocutaneous flap. No neurologic events occurred perioperatively or during the follow-up period of 3 to 50 months. Computed tomography and arteriography were unreliable in predicting tumor involvement of the carotid artery. Three patients died during the study--two of unrelated causes, and one of metastases. None of the patients showed evidence of local recurrence from 3 to 50 months. In two of four wound infections the carotid artery graft was exposed. This was successfully treated by a myocutaneous flap. The mean survival for the group was 18 months. Resection and in-line bypass grafting of the carotid artery invaded by cancer can safely be performed in irradiated and potentially infected fields.

True ablation of atheromatous plaques with laser energy. A phase I safety study

A laser system coupling pulsed dye laser to a 2-mm fiberoptic catheter with incorporated angioscope has been developed for recanalization of occluded arteries. Nine patients with superficial femoral artery occlusions of 4.5 to 49 cm in length were operated on and the recanalized artery harvested for pathologic examination. There were two arterial perforations. The ease of recanalization was determined by plaque composition. Heavily calcified and yellow fibro-fatty lesions were rapidly removed. Smooth white fibrous lesions resisted laser ablation. Direct angioscopy often disclosed discontinuous areas of occlusion that were more susceptible to recanalization. These were not seen on preoperative arteriograms. Microscopic examination of the specimens showed a central core of ablation. There was no evidence of acute damage to the vessel wall, with intact internal elastic lamina demonstrated in the recanalized segments. It appears that fibrous lesions will require a different laser for ablation; however, the delivery/angioscope systems function satisfactorily.

Lower extremity vascular trauma: a comprehensive, aggressive approach

During this study, 25 patients (26 limbs) incurred 37 vascular injuries to the lower extremity. The majority were young males injured by penetrating trauma (84%). There were 25 arterial and 12 venous injuries (two isolated). Sixteen patients had soft-tissue injuries, 12 had fractures, and six had peroneal nerve damage. Twenty-two arterial injuries were repaired, the majority (17) by saphenous vein bypass. Three tibial vessels were ligated. All major venous injuries were repaired. No synthetic material was used. Vascular repair took precedence in all but two cases. After repair, the vascular surgeon assisted with stabilization. Thirteen limbs required fasciotomy; nine required subsequent debridements and later plastic reconstruction. Limb salvage was 96%. More important, 21 patients can ambulate independently on the injured extremity (84%). These results support an aggressive approach to lower extremity vascular trauma with repair of all major arterial and venous injuries in conjunction with aggressive debridement and soft-tissue repair.

Carotid plaque morphology: correlation of duplex sonography with histology

This study attempted to determine whether images obtained during preoperative duplex scanning correlated with histologic studies of carotid endarterectomy plaque and, therefore, might be useful in subsequent studies of the importance of plaque morphology and intraplaque hemorrhage. Forty-six endarterectomy specimens from 44 patients with satisfactory preoperative images were evaluated. The plaques were marked for orientation at the time of removal, and each plaque was imaged by duplex scanning in a saline bath. Magnification radiographs were made. Specimens were embedded in paraffin and slices 6 mu thick were made for staining with hematoxylin and eosin, Masson's trichrome, a modified Verhoeff-vanGieson stain, and von Kossa's stain. Overall, correlation between the preoperative images and the histologic specimens were good to excellent in 42 of 46 specimens. Scanning did not identify three cases of extensive recent intraplaque hemorrhage, however, and one instance of plaque calcification was missed. We conclude that duplex images correlate well with histologic studies except in some cases of recent intraplaque hemorrhage. Duplex imaging is valuable in the correlation of plaque morphology with symptoms for long-term studies. The accuracy of the technique may be improved by using post-processing on static images and in vitro scanning of endarterectomy specimens.

A temporary distal arteriovenous fistula improves venous hemodynamics in a model of venous occlusion

The formation of a temporary distal arteriovenous fistula (dAVF) has been used clinically to palliate patients with symptomatic venous hypertension. This study tested the efficacy of a temporary dAVF for the treatment of venous hypertension in an experimental model. Twenty-four New Zealand white rabbits were divided into two experimental groups. Group I rabbits (n = 12) underwent standardized ligation of the iliac and femoral venous systems. Group II rabbits (n = 12) underwent standardized ligation of the iliac and femoral venous systems with the formation of a temporary dAVF. Venous obstruction was documented with venography, and venous hypertension was documented with femoral venous pressure measurements. Venous pressure, resistance, blood flow, vein circumference, vein cross-sectional area, vein wall thickness, and venography were compared between four rabbits from each group at 2, 4, and 8 weeks. The effect of differences in baseline venous pressures was eliminated by subtracting the venous pressure in the unobstructed rabbit limb from the pressure in the obstructed rabbit leg. Group II rabbits had a lower standardized venous pressure (4.4 +/- 2.2 versus 9.5 +/- 4.2 mm Hg, p less than 0.01) and venous outflow resistance (0.16 +/- 0.08 versus 0.36 +/- 0.18, p less than 0.05) than did group I rabbits. Group II rabbits also had a larger superficial femoral vein circumference (3.46 +/- 0.67 versus 2.57 +/- 0.08 mm, p less than 0.05) and cross-sectional area (0.66 +/- 0.31 versus 0.31 +/- 0.09 mm2, p less than 0.01) than did group I rabbits. The improvement persisted throughout the 6-week study, which suggested an improved venous outflow.

Percutaneous transluminal angioplasty and valvectomy in a failing in situ saphenous graft

A patient is described who experienced increasing ischemia in the follow-up period of femoral-peroneal artery graft surgery. Transcatheter angiographic management was successful in improving the long-term patency of the graft. The procedure is described, and the applications are discussed.

Chronic contained rupture of abdominal aortic aneurysms

Anecdotal reports of chronic contained rupture of abdominal aortic aneurysms exist. Their existence and implications have been largely ignored. From March 1984 to March 1985, 24 patients required repair of an infrarenal abdominal aortic aneurysm. Four patients underwent emergent repair. The remaining 20 patients were evaluated with computed tomography electively. Seven patients (35%) were demonstrated to have a rupture of the aneurysm and a retroperitoneal hematoma on the computed tomographic scan. All of the patients had histories of back or flank pain; five patients continued to complain of mild pain on admission. In no case was shock, impending shock, or a decrease in the hemoglobin level present on admission. All patients were operated on within 24 hours of evaluation. At operation, rupture was noted with organized hematoma outside the aorta contained in a pseudoaneurysmal wall of retroperitoneal connective tissue. There was no intraperitoneal blood. There was no operative mortality and survival was 100% at six months. The CT scan evaluation had identified a subgroup of patients with aneurysms associated with chronic contained rupture.

Restenosis following carotid endarterectomy. Evaluation by duplex ultrasonography

This study evaluated the efficacy of duplex ultrasonographic scanning in assessing the status of carotid arteries after 155 endarterectomies in 131 patients. Duplex studies were done as early as one month and as late as 96 months postoperatively; 33 patients had serial studies. Only 59 (42%) of 142 arteries had no evidence of irregularity or reduction in diameter at the operative site. An additional 41 (29%) had a reduction in diameter between 10% and 29%; 19 (13%) had reductions of 30% to 49%; nine (6%) from 50% to 69%; six (4%) from 70% to 99%; and eight (6%) were occluded. In 51 vessels, angiographic studies confirmed the duplex findings. Symptoms suggestive of recurrent cerebrovascular disease occurred postoperatively in 25 instances; in only three were the anatomic findings suggestive of lesions appropriate to the symptoms. We conclude that duplex ultrasonographic scanning is a useful technique for assessing carotid arteries after endarterectomy and that postoperative narrowing of vessels occurs more commonly than suspected.

Aggressive surgical management of popliteal artery aneurysms

One hundred fifty-nine patients with 244 popliteal aneurysms underwent 167 reconstructive procedures. Patients were divided into those with asymptomatic aneurysms, those with acute ischemia secondary to thrombosis or embolism, those with claudication secondary to chronic thrombosis or embolism, and those with local symptoms referable to the aneurysm itself. Patients who underwent successful revascularization were considered to have good early results. Patients with asymptomatic aneurysms had uniformly good results (97.2 percent) as opposed to those presenting with acute (70.7 percent) or chronic symptoms (83.8 percent). Similar statistically significant differences were seen when patients with thrombosis (71.7 percent) or embolism (81.3 percent) were compared with asymptomatic patients. Analysis of late results indicates that if an initial good result was obtained, the late patency rate was independent of type of presentation. Late results were affected by type of conduit employed where life table analysis showed the superiority of saphenous vein over Dacron prosthesis. At 5 year follow-up, 77.2 percent of all saphenous veins were patent whereas only 29.5 percent of Dacron prostheses remained patent.

Deep venous thrombophlebitis following aortoiliac reconstructive surgery

One hundred patients undergoing elective aortic surgery were scanned prospectively for development of deep venous thrombosis (DVT). The incidence of DVT in this population was 13%. Eleven patients showed only calf vein thrombosis on venography, whereas two had occlusive iliofemoral thrombus. The correlation between venous Doppler ultrasound and venography was 80%. More importantly, Doppler examination correctly identified both patients with occlusive thrombus. Fibrinogen scanning was associated with a false-positive rate of 31%. Only one patient suffered a nonfatal pulmonary embolus. Fibrinogen scanning has an unacceptably high false-positive rate; however, Doppler ultrasound will identify significant occlusive thrombus without a high false-positive rate. The low incidence of pulmonary emboli does not warrant such definitive measures as prophylactic vena caval interruption.