Synthesis and study of 5'-ester prodrugs of N6-cyclopentyladenosine, a selective A1 receptor agonist.

PURPOSE: A series of 5'-esters of N6-cyclopentyladenosine (CPA) were prepared with the aim to improve stability and bioavailability of selective A1 agonists. Log P values, stability, affinity, and activity toward human adenosine A1 receptors were evaluated. METHODS: An appropriate synthetic procedure was adopted to avoid concomitant deamination at position 6. Log P values were obtained by the Mixxor system. The stability of CPA and its 5'-ester was evaluated in human plasma and whole blood and analyzed with high-performance liquid chromatography. The affinities to human A1 receptor expressed by N6-cyclohexyladenosine cells were obtained by binding experiments. The activities were evaluated by measurements of the inhibition of forskolin stimulated 3'-5'-cyclic adenosine monophosphate, performing competitive binding assays. RESULTS: All prodrugs were more lipophilic than CPA, and their hydrolysis, in whole blood and in plasma, was found related, respectively, to the length and hindrance of 5'-substituents. Affinity and activity values indicated a very weak interaction toward adenosine A1 receptor of the intact prodrugs. CONCLUSIONS: We propose 5'-esters of CPA, characterized by suitable lipophilicity and elevated degree of stability in physiological fluids, as possible candidates for CPA prodrugs.

2'-O-Acyl/alkyl-substituted arabinosyl nucleosides as inhibitors of human mitochondrial thymidine kinase.

Introduction of a bulky lipophilic acyl entity at the 2'-OH position of both 1-beta-D-arabinofuranosylthymine (araT) and (E)-5-(2-bromovinyl)-1-beta-D-arabinofuranosyluracil (BVaraU), consistently resulted in a marked ( approximately 10-fold) increase in the inhibitory activity of these new arabinosyl nucleoside analogues for the mitochondrial thymidine kinase (TK-2)-catalysed conversion of 2 microM [methyl-(3)H]dThd to [methyl-(3)H]dTMP. The most potent derivatives were inhibitory to [methyl-(3)H]dThd phosphorylation by TK-2 within the lower micromolar concentration range. Substitution of the arabinosyl nucleoside derivatives with the acyl groups also dramatically increased the selectivity of these compounds. The inhibitory activity of araT and BVaraU to dThd phosphorylation by other related nucleoside kinases, including herpes simplex virus type 1 TK, varicella-zoster virus TK, and cytosolic TK-1, was completely annihilated upon 2'-O-acyl substitution (IC(50) > or = 1000 microM). Kinetic analysis revealed purely competitive inhibition of 2'-O-acyl-BVaraU against TK-2-catalysed thymidine phosphorylation (K(i)/K(m): 2.3). However, 2'-O-acyl-BVaraU was extremely poorly converted to the corresponding arabinosyl nucleoside 5'-monophosphate by TK-2 as revealed by [gamma-(32)P]phosphate transfer studies from [gamma-(32)P]ATP. Thus, the 2'-O-acyl derivatives of BVaraU did not behave as substrates, but rather as potent and highly selective inhibitors of TK-2. This is the first report on such a highly selective arabinosyl nucleoside inhibitor of mitochondrial TK-2, and opens perspectives for the rational design of selective mitochondrial TK-2 inhibitors.

Pyrazole related nucleosides 5. Synthesis and biological activity of 2'-deoxy-2',3'-dideoxy- and acyclo-analogues of 4-iodo-1-beta-D-ribofuranosyl-3-carboxymethyl pyrazole (IPCAR).

Continuing our studies on the structure-activity relationships (SAR) of 4-iodo-1-beta-D-ribofuranosyl-3-carboxymethyl pyrazole (IPCAR), the ribofuranosyl moiety has been substituted with acyclic chains, namely 1-[(2-hydroxyethoxy)methyl]- and 1-[(1,3-dihydroxy-2-propoxy)methyl]-pyrazole derivatives (4, 5 and 8, 9 respectively), with the 2'-deoxy-beta-D-ribofuranosyl group (12 and 13) and finally with the 2',3'-dideoxy-D-glycero-pentofuranosyl-moiety (16 and 17). None of the new compounds display any interesting biological activity.

Peptide T-araC conjugates: solid-phase synthesis and biological activity of N4-(acylpeptidyl)-araC.

Due to the capability of peptidyl derivatives of araC to behave as prodrugs of this antimetabolite, and because of the well known biological properties of peptide T and its analogues (in particular that of targeting CD4+ cells), new peptide T-araC conjugates were prepared and tested in vitro for antiproliferative activity. The aim was that of specifically delivering the antitumor drug to CD4+ cells. N4-(Acylpeptidyl)-derivatives of araC were synthesized by a new general approach involving solid-phase synthesis, which allows mild conditions, avoids the usually required protection of the glycoside portion of nucleosides and affords high yields of the final products. After the demonstration that peptide T-araC conjugates were able to activate chemotaxis by binding CD4 receptor on monocyte membranes, the antiproliferative activity was evaluated against a panel of leukemia lymphoma and carcinoma cell lines derived from human tumors, three CD4+ cell lines included. Title compounds resulted effective as antiproliferative agents at concentrations 4- to 10-fold higher than those of araC alone, did not preferentially inhibit CD4+ cells and proved stable not only in cell culture medium containing 20% FCS, but also in human plasma. All this suggests their potential utility in vivo.

Prodrugs of Ara-CMP and Ara-AMP with a S-acyl-2-thioethyl (SATE) biolabile phosphate protecting group: synthesis and biological evaluation.

The bis(S-pivaloyl-2-thioethyl) phosphotriesters of Ara-C and Ara-A were synthesized as potential bioreversible mononucleotide prodrugs. Some N- and O-acylated derivatives were also prepared with the aim to modify the lipophilicity of the title pronucleotides. Compounds were tested for their antitumor/antiviral activity against a variety of tumor cells and viruses.

Synthesis, cytostatic activity and inhibition of ribonucleotide reductase by 5'-phosphoramidates and 5'-diphosphates, of 2'-O-allyl-arabinofuranosyl nucleosides.

The diphosphates of a series of 2'-O-allyl-1-beta-D-arabinofuranosyl derivatives, previously obtained by us, have been prepared and tested for their inhibitory activity in an in vitro assay using R1 and R2 subunits of the purified recombinant mouse ribonucleotide reductase (RNR). 2'-O-Allyl-araU diphosphate proved to be inhibitory, with an IC50 of 100 microM. The 5'-phosphoramidate pronucleotide of 2'-O-allyl-araU was also prepared and tested for inhibition of tumor cell proliferation.

5'-Phosphoramidates and 5'-diphosphates of 2'-O-allyl-beta-D-arabinofuranosyluracil, -cytosine, and -adenine: inhibition of ribonucleotide reductase.

Continuing our studies on ribonucleotide reductase (RNR) mechanism-based inhibitors, we have now prepared the diphosphates (DP) of 2'-O-allyl-1-beta-D-arabinofuranosyl-uracil and -cytosine and 2'-O-allyl-9-beta-D-arabinofuranosyl-adenine and evaluated their inhibitory activity against recombinant murine RNR. 2'-O-Allyl-araUDP proved to be inhibitory to RNR at an IC(50) of 100 microM, whereas 2'-O-allyl-araCDP was only marginally active (IC(50) 1 mM) and 2'-O-allyl-araADP was completely inactive. The susceptibility of the parent nucleosides to phosphorylation by thymidine kinase and 2'-deoxycytidine kinase was also investigated, and all nucleosides proved to be poor substrates for the above-cited kinases. Moreover, prodrugs of 2'-O-allyl-araU and -araC monophosphates, namely 2'-O-allyl-5'-(phenylethoxy-L-alanyl phosphate)-araU and -araC, were prepared and tested against tumor cell proliferation but proved to be inactive. A molecular modeling study has been conducted in order to explain our results. The data confirm that for both the natural and analogue nucleoside diphosphates, the principal determinant interaction with the active site of RNR is with the diphosphate group, which forms strong hydrogen bonds with Glu623, Thr624, Ser625, and Thr209. Our findings indicate that the poor phosphorylation may represent an explanation for the lack of marked in vitro cytostatic activity of the test compounds.

Standard interleukin-2 (IL-2) and interferon-alpha immunotherapy versus an IL-2 and 4-epirubicin immuno-chemotherapeutic association in metastatic renal cell carcinoma.

BACKGROUND: Recombinant human interleukin-2 (IL-2) has a well-documented anti-tumor activity against RCC and has demonstrated a synergistic anti-tumor activity between doxorubicin and IL-2, thus providing better survival. This study investigated the toxicity and efficacy of the association between doxorubicin and IL-2, and interferon-alpha, and the immuno-chemotherapeutic association with IL-2 and 4-Epirubicin. PATIENTS AND METHODS: Patients with histologic evidence of metastatic or advanced RCC were randomized to receive either IL-2 + IFN-alpha (Arm A) or IL-2 + 4-Epi (Arm B). Arm A patients received IFN-alpha subcutaneously at doses of 3 million UI on days 1, 3 and 5 for 6 weeks. Arm B patients received 4-EPI at doses of 25 mg/m2 on days 1, 8, 15, 22, 29 and 36. Treatment cycles were repeated at 10 week intervals. RESULTS: Of 38 evaluable patients, we observed 2 complete responses, 2 partial responses, 1 minimal response, 1 mixed response, 21 stationary disease and 11 disease progressions. There was no significant difference in overall survival between the two groups. However in arm B, the median overall survival for responding patients was better than that of patients who experienced a disease progression. Performance status was the only predictive prognostic factor. CONCLUSIONS: Our analysis confirms the low response rate associated with IL-2 treatments but seems to indicate a role of anthracycline in improving the survival of responding patients with an acceptable toxicity.

Dose intensification of mitoxantrone in combination with levofolinic acid, fluorouracil, cyclophosphamide and granulocyte colony stimulating factor support in advanced untreated breast cancer patients. A multicentric phase II study of the Southern Italy Oncology Group.

Fifty-five consecutive patients with metastatic breast cancer (MBC) (n = 57) were treated with a combination of levofolinic acid (I-FA) 100 mg/m2 plus 5-fluorouracil (5-FU) 340 mg/m2 i.v. on day 1-3, cyclophosphamide (CTX) 600 mg/m2 i.v. on day 1 and mitoxantrone (DHAD) 12 mg/m2 i.v. on day 1. DHAD dose was progressively escalated by 2 mg/m2/cycle up to 18 mg/m2 in the absence of dose-limiting toxicities. Granulocyte colony stimulating factor (G-CSF) was given s.c. in order to prevent neutropenia. DHAD dosage could be increased to 18 mg/m2 in 66 out of 317 cycles of chemotherapy (21%). In most patients the dose-limiting toxicity was represented by myelosuppression. A statistically significant correlation was found between median white blood cell (WBC) or absolute neutrophil count (ANC) nadir and DHAD dose level. Moreover, a statistically significant correlation was observed between the number of chemotherapeutic cycles, nadir ANC and WBC, and the occurrence of anemia and thrombocytopenia of increasing severity. These data suggest the occurrence of progressive cumulative bone marrow toxicity. Although patients who reached different DHAD levels showed differences in mean dose intensity, such differences were not statistically significant. No correlation was found between the increase in dose intensity and type, rate or duration of objective responses. In patients with metastatic breast cancer the overall response rate was 72% (95% CL 57-84%) with a 18% complete response rate. Median duration of response was 12 and 11 months, respectively, for complete and partial responses. Projected median survival of the whole series of patients with MBC was 18 months. These data demonstrate that the combination of 5-FU with I-FA, CTX and DHAD is very active against MBC. G-CSF use allows the increase DHAD dosage up to 18 mg/m2/cycle, but its use may be linked to the occurrence of sometimes severe cumulative hematological toxicity.

Epidoxorubicin and double biochemical 5-fluorouracil modulation with folinic acid and human lymphoblastoid interferon in advanced gastric carcinoma: a multicentric phase II study of the Southern Italy Oncology Group (GOIM).

In our previous randomized trial of advanced gastric cancer patients, the addition of epirubicin (EPI) to 5-fluorouracil (FU) with folinic acid (FA) resulted in an improved response rate and survival in the responder patients. Preclinical studies also showed an enhancement of FU and anthracyclines with interferon. To evaluate the possibility of human lymphoblastoid interferon (IFN) to enhance the therapeutic activity of the FA-FU + EPI combination regimen, 39 advanced gastric cancer patients received: FU at 375 mg/m2 i.v. immediately after FA (l-isomer form) at 100 mg/m2 i.v. for 5 consecutive days; EPI at 60 mg/m2 i.v. on day 1, and IFN 3 MU s.c. for 7 consecutive days, starting 2 days before the FA-FU administration. Thirty-seven patients were evaluable for response and toxicity. Twelve partial responses were observed with an overall response rate of 32% (95% CI, 17-48%). The median response duration was 6 months, and the median survival time was 8 months. Toxicity was mild and no grade 4 side effects or treatment-related deaths were observed. However, the addition of IFN to the FA-FU + EPI regimen did not improve response, duration of response or survival.

Treatment of advanced urothelial carcinoma with M-VECA (methotrexate, vinblastine, epirubicin and carboplatin).

Transitional cell carcinoma of the urinary tract is actually considered very sensitive to cisplatin-containing regimens. Nevertheless, the generally impaired renal function and poor performance status of these patients are responsible for the severe toxicity usually occurring when cisplatin, either alone or in combination with other agents, is administered to these patients. The aim of this study was to verify the possibility of substituting carboplatin for cisplatin, and epirubicin for doxorubicin in the M-VAC regimen in order to reduce toxicity and improve patient tolerance. Thirty-five patients with advanced urothelial tract carcinoma were treated with a chemotherapeutic regimen composed of methotrexate (30 mg/m2 iv on days 1, 15, 22), vinblastine (3 mg/m2 iv on days 2, 15, 22), epirubicin (35 mg/m2 iv on day 2) and carboplatin (250 mg/m2 iv on day 2) every 4 weeks (M-VECA). All patients had bidimensionally measurable disease. Of the 32 evaluable patients, 5 (16%) obtained a complete response and 10 (31%) a partial response (response rate: 47% C.I. = 30%-64%). Grade III-IV leuko-thrombocytopenia was observed in 25%, and mucositis in 19% of cases. Nevertheless, recovery was prompt and opportune dosage reductions avoided severe toxicity in subsequent cycles in most patients. In conclusion, M-VECA is a safe and effective regimen for the treatment of patients with metastatic urothelial tumors.

Laevofolinic acid, 5-fluorouracil, cyclophosphamide and escalating doses of epirubicin with granulocyte colony-stimulating factor support in locally advanced and/or metastatic breast carcinoma: a phase I-II study of the Southern Italy Oncology Group (GOIM).

Sixty-four consecutive patients with locally advanced (n = 7) or metastatic breast cancer (n = 57), were treated with a combination of laevofolinic acid 100 mg m-2 plus 5-fluorouracil 340 mg m-2 i.v. on days 1-3, cyclophosphamide 600 mg m-2 i.v. on day 1 and epirubicin 90 mg m-2 i.v. on day 1. Epirubicin dose was progressively escalated by 10 mg m-2 per cycle up to 120 mg m-2 in the absence of dose-limiting toxicities. Granulocyte colony-stimulating factor (G-CSF) was given subcutaneously in order to prevent neutropenia. Epirubicin dosage could be increased to 100 mg m-2 in 53 patients (87%), to 110 mg m-2 in 31 patients (51%) and to 120 mg m-2 in 18 cases (30%). In most patients the dose-limiting toxicity was represented by myelosuppression. A statistically significant correlation was found between median white blood count (WBC) or absolute neutrophil count (ANC) nadir and epirubicin dose level (P = 0.009; P = 0.008). Moreover, a statistically significant correlation was observed between the number of chemotherapeutic cycles, nadir ANC and WBC and the occurrence of anaemia and thrombocytopenia of increasing severity. These data suggest the occurrence of progressive cumulative bone marrow toxicity. Although patients who reached different epirubicin levels showed differences in mean dose intensity, such differences were not statistically significant. No correlation was found between the increase in dose intensity and type, rate or duration of objective responses. In patients with metastatic breast cancer the overall response rate was 72% (95% CL 66-78%) with a 25% complete response rate. Median duration of response was 10 and 13 months respectively for complete and partial responses. All patients with locally advanced breast cancer had an objective response and underwent radical mastectomy. Projected median survival of the whole series of patients with metastatic breast cancer was 20 + months. These data demonstrate that the combination of 5-fluorouracil with laevofolinic acid, cyclophosphamide and epirubicin is very active against metastatic breast cancer. Use of G-CSF allows epirubicin dosage to be increased up to 120 mg m-2 cycle-1, but its use may be linked to the occurrence of sometimes severe cumulative haematological toxicity.

Results of a clinical multicentric randomized phase-ii study of nonsmall cell lung-cancer treated with vinorelbine Cisplatin versus vinorelbine alone.

From July 1992 to December 1993, 62 patients with non-small cell lung cancer (NSCLC) were admitted to a multicentric randomized study. The patients were treated with vinorelbine (V) alone at a dose of 25 mg/m(2)/i.v. weekly or with V at a dose of 25 mg/m(2)/i.v. on day 1 and 8 plus cisplatin at a dose of 80 mg/m(2)/i.v. on day 1 every 3-4 weeks (VP). An objective response was observed in 42% of patients treated with VP versus 12.5% of those treated with vinorelbine alone (p=0.038). There was no significant difference in the median survival duration between the two groups (38 versus 30 weeks for VP and V, respectively). Toxicity was tolerable but more severe in the VP regimen. These data suggest that V is an active agent in NSCLC and that the VP regimen may yield results comparable to other cisplatin combinations for treatment of these tumors.