Identification of novel and potent synthetic TLR agonists

Agonists and antagonists of Toll-like receptors (TLRs) may be useful as vaccine adjuvants or suppressors of inflammation, respectively. In an effort to identify compounds capable of activating macrophages via TLRs or other sensors, a synthetic compound library was screened using mouse peritoneal macrophages and human THP-1 cells. Through extensive SAR studies of initial hits, we developed two strong synthetic agonists: Neoseptin-3 and Diprovocim. Genetic studies established that neoseptin-3 is a mouse TLR4/MD-2 agonist with no structural similarity to LPS. It activates mTLR4/MD-2 independently of CD14 and triggers canonical MyD88- and TRIF-dependent signaling. Diprovocim was found by a combination of genetic and antibody blockade analyses to be a TLR1/2 agonist, active on both mouse and human receptors. Its EC50 in human THP-1 cells is 110 pM. Diprovocim showed TLR1/2 dependent adjuvant activity when co-administered with ovalbumin (OVA). It not only promoted antigen-specific humoral responses but also activated cytotoxic T lymphocyte responses in a TLR1/2 dependent manner. Since neither Neoseptin-3 nor Diprovocim resemble the natural ligands for TLR4/MD-2 nor TLR1/2, respectively, we surmise that other “unconventional” ligands for these TLRs may exist in nature. However, the exquisite SAR of both compounds makes it clear that TLRs are not highly promiscuous receptors; on the contrary, they are activated only by compounds that fulfill strict structural rules. In finding these agonists, we also identified antagonists that bind the TLR complexes but do not activate them. The parent compounds Neoseptin-3 and Diprovocim will be used to develop new agonists and antagonists optimized for clinical application.

Structural characterization of TLRs with novel agonists

Small molecule TLR4 and TLR2 agonists have been reported, but no structural data reveals their activation mechanism and detailed interactions with the TLRs. We have developed two small molecule agonists, Neoseptin-3 and Diprovocim, that activate TLR4/MD-2 and TLR1/TLR2 complexes, respectively, with exquisitely specific structure activity relationships. These two molecules bear no structural similarity to the natural ligands, lipopolysaccharide (LPS) and tri-acylated lipopeptide (Pam3CSK4). The crystal structures of Neoseptin-3 in complex with mouse TLR4/MD-2 and Diprovocim in complex with human TLR2 provide the first glimpse of how these TLRs bind to unconventional agonists, revealing unique and unexpected binding modes. Neoseptin-3 binds as an asymmetrical dimer within the hydrophobic pocket of MD-2, and induces an active receptor complex (a dimer of TLR4/MD-2) similar to that induced by lipid A. However, Neoseptin-3 and lipid A form different molecular contacts with TLR4/MD-2 to achieve receptor activation. Diprovocim forms a symmetrical dimer and interacts with the same hydrophobic pocket of TLR2 as Pam3CSK4, inducing homodimerization of TLR2 that has a different conformation than the active TLR1/TLR2 heterodimer. Diprovocim binds to TLR2 through an extensive intermolecular hydrogen bonding network that is not observed in the Pam3CSK4/TLR2/TLR1 structure. These two structures are now guiding us in optimization of TLR4/MD-2 and TLR1/TLR2 agonists and antagonists for clinical applications.

Evaluation of a reductively activated duocarmycin prodrug against murine and human solid cancers

In treating cancer with clinically approved chemotherapies, the high systemic toxicity and lack of selectivity for malignant cells often result in an overall poor response rate. One pharmacological approach to improve patient response is to design targeted therapies that exploit the cancer milieu by reductively activating prodrugs, which results in the selective release of the free drug in the tumor tissue. Previously, we characterized prodrugs of seco-CBI-indole 2 (CBI-indole 2) designed to be activated in hypoxic tumor microenvironments, wherein the tumor maintains higher concentrations of "reducing" nucleophiles capable of preferentially releasing the free drug by nucleophilic attack on a weak N-O bond. Of these prodrugs, BocNHO-CBI-indole 2 (BocNHO) surpassed the efficacy of the free drug, CBI-indole 2, when examined in vivo in the murine L1210 leukemia model and demonstrated reduced toxicity suggesting a targeted or sustained release in vivo. Herein, we further examine the biological activity of the BocNHO prodrug in murine breast cancer, as well as human prostate and lung cancer cell lines, in vitro. Notably, BocNHO manifests potent antiproliferative and cytotoxic activity in all three tumor cell lines. However, in comparison to the activity observed in the murine cancer cell line, the human cancer cell lines were less sensitive, especially at early timepoints for cytotoxicity. Based on these findings, BocNHO was tested in a more clinically relevant orthotopic lung tumor model, revealing significant efficacy and reduced toxicity compared with the free drug. The data suggests that this pharmacological approach to designing targeted therapies is amenable to human solid tumors.

The mechanism of action of ramoplanin and enduracidin

The lipoglycodepsipeptide antibiotic ramoplanin is proposed to inhibit bacterial cell wall biosynthesis by binding to intermediates along the pathway to mature peptidoglycan, which interferes with further enzymatic processing. Two sequential enzymatic steps can be blocked by ramoplanin, but there is no definitive information about whether one step is inhibited preferentially. Here we use inhibition kinetics and binding assays to assess whether ramoplanin and the related compound enduracidin have an intrinsic preference for one step over the other. Both ramoplanin and enduracidin preferentially inhibit the transglycosylation step of peptidoglycan biosynthesis compared with the MurG step. The basis for stronger inhibition is a greater affinity for the transglycosylase substrate Lipid II over the MurG substrate Lipid I. These results provide compelling evidence that ramoplanin's and enduracidin's primary cellular target is the transglycosylation step of peptidoglycan biosynthesis.

Computed axial tomography in C1-C2 trauma

Twenty patients with C1-C2 vertebral trauma underwent computed tomographic (CT) scans to evaluate prospectively its efficiency for diagnosis and treatment. It is suggested that if standard roentgenograms are inconclusive, CT scan is recommended for further evaluation of C1 fractures and C1-C2 rotatory subluxation in preference to tomography and cineradiography. CT scans do not assess dynamic stability and may miss minimally displaced odontoid fractures. It was also concluded that they add little in the treatment of hangman's fractures, although scanning did show that the pathology was often more complex than anticipated. The clinician must be aware of the capabilities and the limitations of the specific scanner in use and work closely with the radiologist to maximize the yield of information. The CT scan is very helpful as an adjunct to standard x-ray studies, but is not recommended as a screening procedure.

New traction devices to aid reduction of shoulder dislocations

A set of traction devices that aid in the reduction of shoulder dislocations is described and their use and efficiency are discussed. A series of 47 consecutive patients seen over a six-month period and diagnosed as having shoulder dislocations with no other major trauma composed the study population. After radiographic confirmation and premedication with analgesics and muscle relaxants, the devices were used. The traction- countertraction method was used initially. When this method was unsuccessful, the Stimson method was performed using an alternate traction strap. These devices were successful in 96% of the relocations attempted. No complications were encountered. The traction devices were found to be effective and easy to use.

Sonography in the diagnosis and management of hepatic amebic abscess in children

Hepatic amebic abscess is a potentially fatal infection which is difficult to diagnose in children. Sonography is an ideal non-invasive imaging tool which can prove invaluable in the diagnosis and management of hepatic amebic abscess. Sonographic findings should suggest the correct diagnosis in most instances. This allows prompt initiation of therapy, forestalling life-threatening complications. Sonography is also an extremely useful non-invasive means of following response to therapy in children with hepatic amebic abscesses.

Gray scale ultrasonography of a traumatic biliary cyst

Traumatic hepatic biliary cysts, which occur when there is leakage after traumatic disruption of the biliary system, can be readily detected with hepatic sonography. Differentiation from other hepatic fluid collections can be made by percutaneous thin needle aspiration. Aspiration may have possible utility as a therapeutic modality. A case is presented in which Gray scale ultrasonography revealed a biliary cyst which was drained operatively and resolved.

Ultrasonographic demonstration of renal cell carcinoma in a pelvic kidney

Renal cell carcinoma in pelvic kidneys is a surprisingly rare entity. This case report describes the first instance in which the tumor was delineated ultrasonographically. No clear rationale for this apparently lower incidence can be determined.

CT of inflammatory disease of the psoas muscle

Computed tomography (CT) findings in eight cases of psoas inflammatory disease are described retrospectively. Because of its exquisite retroperitoneal imaging capabilities, CT proved to be an ideal tool in evaluating suspected disease in this area. Clinically, the deep position of psoas abscesses has made diagnosis problematic. In addition, many radiographic signs of psoas inflammation have provided only indirect evidence, such as displacement of the ureter or alteration of the psoas margin. The organ-specific information available with CT makes detection more efficient and diagnosis more certain. Especially when coupled with percutaneous aspiration biopsy, CT has proved an effective and rapid means of diagnosing and guiding the therapy of psoas abscess.

Severe hydronephrosis and severe renal cystic disease: ultrasonic differentiation

End-stage renal cystic disease and severe hydronephrosis may reveal similar ultrasonographic findings. A "blind analysis" of 13 cases selected on the basis of smiliar extensive end-stage disease (little or no renal parenchyma visualized) was performed. The identification of a dilated renal pelvis was the most reliable ultrasonographic indicator of hydronephrosis. If the renal pelvis cannot be identified, renal cystic disease is the most likely diagnosis. All eight cases of hydronephrosis were correctly identified in this fashion. Four of five cases of severe cystic disease were correctly diagnosed. In one patient a peripelvic cyst was incorrectly interpreted as a dilated renal pelvis leading to the incorrect diagnosis of hydronephrosis. There may be ancillary signs that may help distinguish severe hydronephrosis from severe renal cystic disease. If these signs are not present, the only reliable criterion is whether the renal pelvis is dilated on careful examination of the renal sinus.