The fibroblast growth factor receptor inhibitor, derazantinib, has strong efficacy in human gastric tumor models and synergizes with paclitaxel in vivo.

Derazantinib (DZB) is an inhibitor of fibroblast growth factor receptors 1-3 (FGFR1-3), with additional activity against colony-stimulating-factor-1 receptor (CSF1R). We have profiled the activity of DZB in gastric cancer (GC) as monotherapy and combined with paclitaxel, and explored means of stratifying patients for treatment. The antiproliferative potency of DZB in vitro was quantified in 90 tumor cell lines and shown to correlate significantly with FGFR expression (<0.01) but not with FGFR DNA copy-number (CN) or FGFR mutations. In four GC cell lines in vitro , little or no synergy was observed with paclitaxel. In athymic nude mice, bearing cell-line derived xenografts (CDX) or patient-derived xenograft (PDX) GC models, DZB efficacy correlated highly significantly with FGFR gene expression ( r2 = 0.58; P = 0.0003; n = 18), but not FGFR mutations or DNA-CN. In FGFR-driven GC models, DZB had comparable efficacy to three other FGFR inhibitors and was more efficacious than paclitaxel. DZB had dose-dependent plasma pharmacokinetics but showed low brain penetration at all doses. GC models (one CDX and six PDX) were tested for sensitivity to the combination of DZB and paclitaxel and characterized by immunohistochemistry. The combination showed synergy (5) or additivity (2), and no antagonism, with synergy significantly associated ( P < 0.05) with higher levels of M2-type macrophages. The association of strong efficacy of the combination in vivo with M2 macrophages, which are known to express CSF1R, and the absence of synergy in vitro is consistent with the tumor microenvironment also being a factor in DZB efficacy and suggests additional means by which DZB could be stratified for cancer treatment in the clinic.

Derazantinib, a fibroblast growth factor receptor inhibitor, inhibits colony-stimulating factor receptor-1 in macrophages and tumor cells and in combination with a murine programmed cell death ligand-1-antibody activates the immune environment of murine syngeneic tumor models.

Derazantinib (DZB) is an inhibitor of the fibroblast growth factor receptors 1-3 (FGFRi) with similar potency against colony-stimulating factor receptor-1 (CSF1R), a protein important in the recruitment and function of tumor-associated macrophages. DZB inhibited pCSF1R in the macrophage cell line RAW264.7, and tumor cells GDM-1 and DEL, and had the same potency in HeLa cells transiently over-expressing FGFR2. DZB exhibited similar potency against pCSF1R expressed by isolated murine macrophages, but as in the cell lines, specific FGFRi were without significant CSF1R activity. DZB inhibited growth of three tumor xenograft models with reported expression or amplification of CSF1R, whereas the specific FGFRi, pemigatinib, had no efficacy. In the FGFR-driven syngeneic breast tumor-model, 4T1, DZB was highly efficacious causing tumor stasis. A murine PD-L1 antibody was without efficacy in this model, but combined with DZB, increased efficacy against the primary tumor and further reduced liver, spine and lung metastases. Immunohistochemistry of primary 4T1 tumors showed that the combination favored an antitumor immune infiltrate by strongly increasing cytotoxic T, natural killer and T-helper cells. Similar modulation of the tumor microenvironment was observed in an FGFR-insensitive syngeneic bladder model, MBT-2. These data confirm CSF1R as an important oncology target for DZB and provide mechanistic insight for the ongoing clinical trials, in which DZB is combined with the PD-L1 antibody, atezolizumab.

Derazantinib: an investigational drug for the treatment of cholangiocarcinoma.

INTRODUCTION: This review evaluates the clinical role of fibroblast growth factor receptor 2 (FGFR2) inhibition with derazantinib in patients with intrahepatic cholangiocarcinoma (iCCA) harboring actionable oncogenic FGFR2 fusions/rearrangements, mutations and amplifications. FGFR inhibitors such as derazantinib are currently being evaluated to address the unmet medical need of patients with previously treated, locally advanced or metastatic iCCA harboring such genetic aberrations. AREAS COVERED: We summarize the pharmacokinetics, and the emerging safety and efficacy data of the investigational FGFR inhibitor derazantinib. We discuss the future directions of this novel therapeutic agent for iCCA. EXPERT OPINION: Derazantinib is a potent FGFR1‒3 kinase inhibitor which also has activity against colony stimulating factor-1‒receptor (CSF1R) and vascular endothelial growfth factor receptor‒2 (VEGFR2), suggesting a potentially differentiated role in the treatment of patients with iCCA. Derazantinib has shown clinically meaningful efficacy with durable objective responses, supporting the therapeutic potential of derazantinib in previously treated patients with iCCA harboring FGFR2 fusions/rearrangements, mutations and amplifications. The clinical safety profile of derazantinib was well manageable and compared favorably to the FGFR inhibitor class, particularly with a low incidence of drug-related hand-foot syndrome, stomatitis, retinal and nail toxicity. These findings support the need for increased molecular profiling of cholangiocarcinoma patients.

Propenylamide and propenylsulfonamide cephalosporins as a novel class of anti-MRSA beta-lactams.

Novel C(3) propenylamide and propenylsulfonamide cephalosporins have been synthesized and tested for their ability to inhibit the penicillin-binding protein 2' (PBP2') from Staphylococcus epidermidis and the growth of a panel of clinically relevant bacterial species, including methicillin-resistant Staphylococcus aureus (MRSA). The most potent compounds inhibited the growth of MRSA strains with minimum inhibitory concentrations (MIC) as low as 1 microg/mL. The structure-activity relationship revealed the potential for further optimization of this new cephalosporin class.

A polylinker approach to reductive loop swaps in modular polyketide synthases.

Multiple versions of the DEBS 1-TE gene, which encodes a truncated bimodular polyketide synthase (PKS) derived from the erythromycin-producing PKS, were created by replacing the DNA encoding the ketoreductase (KR) domain in the second extension module by either of two synthetic oligonucleotide linkers. This made available a total of nine unique restriction sites for engineering. The DNA for donor "reductive loops," which are sets of contiguous domains comprising either KR or KR and dehydratase (DH), or KR, DH and enoylreductase (ER) domains, was cloned from selected modules of five natural PKS multienzymes and spliced into module 2 of DEBS 1-TE using alternative polylinker sites. The resulting hybrid PKSs were tested for triketide production in vivo. Most of the hybrid multienzymes were active, vindicating the treatment of the reductive loop as a single structural unit, but yields were dependent on the restriction sites used. Further, different donor reductive loops worked optimally with different splice sites. For those reductive loops comprising DH, ER and KR domains, premature TE-catalysed release of partially reduced intermediates was sometimes seen, which provided further insight into the overall stereochemistry of reduction in those modules. Analysis of loops containing KR only, which should generate stereocentres at both C-2 and C-3, revealed that the 3-hydroxy configuration (but not the 2-methyl configuration) could be altered by appropriate choice of a donor loop. The successful swapping of reductive loops provides an interesting parallel to a recently suggested pathway for the natural evolution of modular PKSs by recombination.

Antipropionibacterial activity of BAL19403, a novel macrolide antibiotic.

BAL19403 exemplifies a new family of macrolide antibiotics with excellent in vitro activity against propionibacteria. MICs indicated that BAL19403 was very active against erythromycin-resistant and clindamycin-resistant propionibacteria with mutations in the region from positions 2057 to 2059 (Escherichia coli numbering) of the 23S rRNA, although it is less active against those rare clinical isolates in which a methyltransferase, ErmX, confers macrolide and lincosamide resistance by dimethylation of the adenine moiety at position 2058. BAL19403 was predominantly bacteriostatic toward the propionibacteria, and population analyses indicated resistance selection frequencies for BAL19403 and the comparator drugs (erythromycin, clindamycin) in the range 10(-8) to 10(-9) for cutaneous propionibacteria with diverse antibiotic resistance profiles. On the basis of its antipropionibacterial activity and its high anti-inflammatory activity, BAL19403 represents a promising topical treatment for mild to moderate inflammatory acne vulgaris.

Activity of the novel macrolide BAL19403 against ribosomes from erythromycin-resistant Propionibacterium acnes.

BAL19403 is a macrolide antibiotic from a novel structural class with potent activity against propionibacteria in vitro. The antibacterial spectrum of BAL19403 covers clinical isolates with mutations in the 2057 to 2059 region of 23S rRNA that confer resistance to erythromycin and clindamycin. The basis of this improved activity was investigated by ribosome binding assays and by a coupled transcription and translation assay. The latter was specifically developed for the use of ribosomes from Propionibacterium acnes. BAL19403 inhibited protein expression by ribosomes from erythromycin-sensitive and erythromycin-resistant P. acnes with similar potencies if the resistance was due to G2057A or A2058G mutations. BAL19403 showed a >10-fold higher activity than erythromycin against ribosomes from a strain with the erm(X) gene. Erm(X) confers high levels of macrolide and lincosamide resistance by dimethylation of A2058. Assays with such ribosomes showed that BAL19403 was potent enough to inhibit half of the total activity with a 50% inhibitory concentration very close to the value measured with erythromycin-sensitive ribosomes. We concluded from our data that the P. acnes strain with the erm(X) gene had a mixed population of ribosomes, with macrolide-sensitive and macrolide-resistant species.

Elucidation of the in vitro metabolic profile of stable isotope labeled BAL19403 by accurate mass capillary liquid chromatography/quadrupole time-of-flight mass spectrometry and isotope exchange.

The in vitro metabolic pattern of BAL19403, a novel macrolide antibiotic, was investigated by capillary liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS) in incubations with human microsomes. For the elucidation of the metabolic pathway, BAL19403 labeled with four deuterium atoms (D4) was used, and detection of metabolites performed using mixtures of the unlabeled (H4) BAL19403 and its D4 analogue (1:1) as substrate. All metabolites appeared with similar chromatographic behavior. MS/MS spectra of BAL19403 and its metabolites are dominated by non-informative fragment ions. Therefore, the structure of the metabolites was elucidated mainly by accurate mass measurements with subsequent proposals of elemental compositions. Main biotransformations were N-demethylation, lactone ring hydrolysis, and oxidation. Additionally, N-dealkylation of the aromatic moiety was identified. This dealkylation results not only in formation of an aldehyde, according to the classical pathway, but also in formation of the corresponding alcohol and carboxylic acid. Final elucidation of their structures was possible, since this dealkylation takes place vicinal to the deuterium-labeled part of BAL19403 and interferes with D/H exchange. The degree of D/H exchange, determined by analysis of the metabolite isotopic pattern, was used to elucidate the adjacent functional group.

Stereochemistry of catalysis by the ketoreductase activity in the first extension module of the erythromycin polyketide synthase.

Multiple ketoreductase activities play a crucial role in establishing the stereochemistry of the products of modular polyketide synthases (PKSs), but there has been little systematic scrutiny of catalysis by individual ketoreductases. To allow this, a diketide synthase, consisting of the loading module, first extension module, and the chain-terminating thioesterase of the erythromycin-producing PKS of Saccharopolyspora erythraea, has been expressed and purified. The DNA encoding the ketoreductase-1 domain in this construct is flanked by unique restriction sites so that another ketoreductase domain can be readily substituted. The purified recombinant diketide synthase catalyzes, at a very low rate (k(cat) equals 2.5 x 10(-3) s(-1)), the specific production of the diketide (2S,3R)-2-methyl-3-hydroxypentanoic acid. The activity of the ketoreductase domain in this model synthase was analyzed using as a model substrate (+/-)-2-methyl-3-oxopentanoic acid N-acetylcysteaminyl (NAC) ester for which k(cat)/K(m) was 21.7 M(-1) s(-1). The NAC thioester of (2S,3R)-2-methyl-3-hydroxypentanoic acid was the major product and was strongly preferred over other stereoisomers as a substrate in the reverse reaction. The bicyclic ketone (9RS)-trans-1-decalone, a known substrate for ketoreductase in fatty acid synthase, was found also to be an effective substrate for the ketoreductase of the diketide synthase. Only the (9R)-trans-1-decalone was reduced, selectively and reversibly, to the (1S,9R)-trans-decalol. The stereochemical course of reduction and oxidation is exactly as found previously for the ketoreductase of animal fatty acid synthase, an additional indication of the close similarity of these enzymes.

Novel ketolide antibiotics with a fused five-membered lactone ring--synthesis, physicochemical and antimicrobial properties.

In an effort to find novel semisynthetic macrolides with extended antibacterial spectrum and improved activity we prepared a series of compounds based on commercially available clarithromycin, a potent and safe antimicrobial agent of outstanding clinical and commercial interest. According to the literature, improvement of antibacterial activity of erythromycin type antibiotics can be achieved by introduction of fused heterocycles such as cyclic carbonates or carbamates at positions 11 and 12 (such as in telithromycin). In the course of the work presented here, a similar, hitherto unprecedented set of compounds bearing a five-membered lactone ring fused to positions 11 and 12 was prepared based on carbon-carbon bond formation via intramolecular Michael addition of a [(hetero)arylalkylthio]acetic acid ester enolate to an alpha,beta-unsaturated ketone as the key step. Some of the ketolide compounds described in this paper were highly active against a representative set of erythromycin sensitive and erythromycin resistant test strains. The best compound showed a similar antimicrobial spectrum and comparable activity in vitro as well as in vivo as telithromycin. Furthermore, some physicochemical properties of these compounds were determined and are presented here. On the basis of these results, the novel ketolide lactones presented in this paper emerged as valuable lead compounds with comparable properties as the commercial ketolide antibacterial telithromycin (Ketek).

Direct production of ivermectin-like drugs after domain exchange in the avermectin polyketide synthase of Streptomyces avermitilis ATCC31272.

Ivermectin, a mixture of 22,23-dihydroavermectin B1a9 with minor amounts of 22,23-dihydroavermectin B1b 10, is one of the most successful veterinary antiparasitic drugs ever produced. In humans, ivermectin has been used for the treatment of African river blindness (onchocerciasis) resulting in an encouraging decrease in the prevalence of skin and eye diseases linked to this infection. The components of ivermectin are currently synthesized by chemical hydrogenation of a specific double bond at C22-C23 in the polyketide macrolides avermectins B1a 5 and B1b 6, broad-spectrum antiparasitic agents isolated from the soil bacterium Streptomyces avermitilis. We describe here the production of such compounds (22,23-dihydroavermectins B1a 9 and A1a 11) by direct fermentation of a recombinant strain of S. avermitilis containing an appropriately-engineered polyketide synthase (PKS). This suggests the feasibility of a direct biological route to this valuable drug.