Intralesional administration of L19-IL2/L19-TNF in stage III or stage IVM1a melanoma patients: results of a phase II study.

The intratumoral injection of cytokines, in particular IL2, has shown promise for cutaneous melanoma patients with unresectable disease or continuous recurrence despite surgery. We recently reported that the intralesional injection of L19-IL2, an immunocytokine combining IL2 and the human monoclonal antibody fragment L19, resulted in efficient regional control of disease progression, increased time to distant metastasis and evidence of effect on circulating immune cell populations. We have also shown in preclinical models of cancer a remarkable synergistic effect of the combination of L19-IL2 with L19-TNF, a second clinical-stage immunocytokine, based on the same L19 antibody fused to TNF. Here, we describe the results of a phase II clinical trial based on the intralesional administration of L19-IL2 and L19-TNF in patients with stage IIIC and IVM1a metastatic melanoma, who were not candidate to surgery. In 20 efficacy-evaluable patients, 32 melanoma lesions exhibited complete responses upon intralesional administration of the two products, with mild side effects mainly limited to injection site reactions. Importantly, we observed complete responses in 7/13 (53.8 %) non-injected lesions (4 cutaneous, 3 lymph nodes), indicating a systemic activity of the intralesional immunostimulatory treatment. The intralesional administration of L19-IL2 and L19-TNF represents a simple and effective method for the local control of inoperable melanoma lesions, with a potential to eradicate them or make them suitable for a facile surgical removal of the residual mass.

Potentiating the activity of rituximab against mantle cell lymphoma in mice by targeting interleukin-2 to the neovasculature.

There is increasing interest in the site-directed pharmacodelivery of therapeutic payloads to the tumor site using antibodies as transport vehicles. Here, we investigated the efficacy of L19-IL2, an antibody-cytokine fusion protein that specifically delivers IL-2 to the tumor site by homing to the extra-domain B of fibronectin (EDB-Fn) expressed on tumor-associated blood vessels, against mantle cell lymphoma (MCL) in mice. L19-IL2 was shown to selectively localize at lymphoma lesions in vivo and to mediate significant lymphoma growth retardation, which was potentiated by co-administration of the anti-CD20 antibody rituximab. When co-injected with rituximab, L19-IL2 induced complete remissions of localized MCL xenografts in 6/8 mice (75%), whereas the combination of rituximab and equivalent doses of non-targeted IL-2 only slightly delayed tumor growth. In disseminated MCL, combination therapy with L19-IL2 and rituximab exhibited a significant survival benefit over treatment with IL-2 and rituximab and completely eradicated the disease in 2/7 cases (28.6%). Mechanistically, histological analyses of post-therapeutic lymphoma tissues revealed a strong intratumoral accumulation of macrophages and natural killer cells after a single dose of the immunocytokine, whereas L19-IL2 had no significant impact on microvessel density or on tissue penetration of co-injected rituximab. Collectively, these results provide the scientific rationale for the clinical evaluation of L19-IL2 in combination with anti-CD20 immunotherapy in patients with MCL.

Targeting interleukin-2 to the bone marrow stroma for therapy of acute myeloid leukemia relapsing after allogeneic hematopoietic stem cell transplantation.

The antibody-based delivery of IL2 to extracellular targets expressed in the easily accessible tumor-associated vasculature has shown potent antileukemic activity in xenograft and immunocompetent murine models of acute myelogenous leukemia (AML), especially in combination with cytarabine. Here, we report our experience with 4 patients with relapsed AML after allogeneic hematopoietic stem cell transplantation (allo-HSCT), who were treated with the immunocytokine F16-IL2, in combination with low-dose cytarabine. One patient with disseminated extramedullary AML lesions achieved a complete metabolic response identified by PET/CT, which lasted 3 months. Two of 3 patients with bone marrow relapse achieved a blast reduction with transient molecular negativity. One of the 2 patients enjoyed a short complete remission before AML relapse occurred 2 months after the first infusion of F16-IL2. In line with a site-directed delivery of the cytokine, F16-IL2 led to an extensive infiltration of immune effector cells in the bone marrow. Grade 2 fevers were the only nonhematologic side effects in 2 patients. Grade 3 cytokine-release syndrome developed in the other 2 patients but was manageable in both cases with glucocorticoids. The concept of specifically targeting IL2 to the leukemia-associated stroma deserves further evaluation in clinical trials, especially in patients who relapse after allo-HSCT.

The tumor-targeting immunocytokine F16-IL2 in combination with doxorubicin: dose escalation in patients with advanced solid tumors and expansion into patients with metastatic breast cancer.

A phase Ib/II trial was performed to evaluate safety, tolerability, recommended dose (RD) and efficacy of F16-IL2, a recombinant antibody-cytokine fusion protein, in combination with doxorubicin in patients with solid tumors (phase Ib) and metastatic breast cancer (phase II). Six patient cohorts with progressive solid tumors (n = 19) received escalating doses of F16-IL2 [5-25 Million International Units (MIU) of IL2 equivalent dose] in combination with escalating doses of doxorubicin (0-25 mg/m(2)) on day 1, 8 and 15 every 4 weeks. Subsequently, patients with metastatic breast cancer (n = 10) received the drug combination at the RD. Clinical data and laboratory findings were analyzed for safety, tolerability, and activity. F16-IL2 could be administered up to 25 MIU, in combination with the RD of doxorubicin (25 mg/m(2)). No human anti-fusion protein antibodies (HAFA) response was detected. Pharmacokinetics of F16-IL2 was dose-dependent over the tested range, with half-lives of ca. 13 and ca. 8 hours for cohorts dosed at lower and higher levels, respectively. Toxicities were controllable and reversible, with no combination treatment-related death. After 8 weeks, 57% and 67% disease control rates were observed for Phase I and II, respectively (decreasing to 43% and 33% after 12 weeks), considering 14 and 9 patients evaluable for efficacy. One patient experienced a long lasting partial response (45 weeks), still on-going at exit of study. F16-IL2 can be safely and repeatedly administered at the RD of 25 MIU in combination with 25 mg/m(2) doxorubicin; its safety and activity are currently being investigated in combination with other chemotherapeutics, in order to establish optimal therapy settings.

Armed antibodies for cancer treatment: a promising tool in a changing era.

Advances in the understanding of tumor immunology and molecular biology of melanoma cells have favored a larger application of immunotherapy and targeted therapies in the clinic. Several selective mutant gene inhibitors and immunomodulating antibodies have been reported to improve overall survival or progression-free survival in metastatic melanoma patients. However, despite impressive initial responses, patients treated with selective inhibitors relapse quickly, and toxicities associated to the use of immunomodulating antibodies are not easily manageable. In this sense, the concept of using antibodies as delivery vehicles for the preferential in vivo localization of the drug at the site of disease with reduction of side effects has raised particular interest. Antibody-cytokine fusion proteins (termed immunocytokines) represent a new simple and effective way to deliver the immunomodulatory payload at the tumor site, with the aim of inducing both local and systemic antitumoral immune responses and limiting systemic toxicities. Several clinical trials have been conducted and are actually ongoing with different immunocytokines, in several tumor histotypes. In metastatic melanoma patients, different drug delivery modalities such as systemic, loco-regional and intratumoral are under investigation. In this review, the rationale for the use of L19-IL2 and L19-TNF, two clinical stage immunocytokines produced by the Philogen group, as well as opportunities for their future development will be discussed.

Intralesional treatment of stage III metastatic melanoma patients with L19-IL2 results in sustained clinical and systemic immunologic responses.

L19-IL2 is a recombinant protein comprising the cytokine IL2 fused to the single-chain monoclonal antibody L19. In previous studies, intralesional injection with IL2 has shown efficacy for the locoregional treatment of cutaneous/subcutaneous metastases in patients with advanced melanoma. The objectives of this study were to investigate whether (i) intralesional delivery of a targeted form of IL2 would yield similar results, with reduction of injection frequency and treatment duration; and (ii) systemic immune responses were induced by the local treatment. Patients with stage IIIB/IIIC melanoma and cutaneous/subcutaneous injectable metastases received weekly intratumoral injections of L19-IL2 at a maximum dose of 10 MIU/week for 4 consecutive weeks. Tumor response was evaluated 12 weeks after the first treatment. Twenty-four of 25 patients were evaluable for therapy-induced responses. A complete response (CR) by modified immune-related response criteria (irRC) of all treated metastases was achieved in 6 patients (25%), with long-lasting responses in most cases (5 patients for ≥24 months). Objective responses were documented in 53.9% of all index lesions [44.4% CR and 9.5% partial responses (by irRC)], and 36.5% of these remained stable, while 9.5% progressed. Toxicity was comparable with that of free IL2, and no serious adverse events were recorded. A significant temporary increase of peripheral regulatory T cells and natural killer cells, sustained increase of absolute CD4(+) lymphocytes, and decrease of myeloid-derived suppressor cells were observed upon treatment. Finally, we recorded encouraging data about the progression time to distant metastases and overall survival.

Radioimmunotherapy with Tenarad, a 131I-labelled antibody fragment targeting the extra-domain A1 of tenascin-C, in patients with refractory Hodgkin's lymphoma.

PURPOSE: The extra-domain A1 of tenascin-C (TC-A1) is highly expressed in the extracellular matrix of tumours and on newly formed blood vessels and is thus a valuable target for radionuclide therapy. Tenarad is a fully human miniantibody or small immunoprotein (SIP, molecular weight 80 kDa) labelled with (131)I that is derived from a TC-A1-binding antibody. Previous phase I/II studies with a similar compound ((131)I-L19SIP) used for radioimmunotherapy (RIT) have shown preliminary efficacy in a variety of cancer types. In this ongoing phase I/II trial, Tenarad was administered to patients with recurrent Hodgkin's lymphoma (HL) refractory to conventional treatments. METHODS: Eight patients (four men, four women; age range 19 - 41) were enrolled between April 2010 and March 2011. All patients had received a median of three previous lines of chemotherapy (range three to six) and seven had also undergone autologous stem cell transplantation (ASCT) or bone marrow transplantation. In addition, seven patients received external beam radiation. All patients had nodal disease, constitutional B symptoms and some showed extranodal disease in skeletal bone (four patients), lung (three), liver (two) and spleen (one). Baseline assessments included whole-body FDG PET with contrast-enhanced CT and diagnostic Tenarad planar and SPECT studies. Patients were considered eligible to receive a therapeutic dose of Tenarad (2.05 GBq/m(2)) if tumour uptake was more than four times higher than that of muscle. RESULTS: All patients were eligible and received the therapeutic dose of Tenarad. Only one patient developed grade 4 thrombocytopenia and leucocytopenia, requiring hospitalization and therapeutic intervention. All other patients had haematological toxicity of grade 3 or lower, which resolved spontaneously. At the first response assessment (4 - 6 weeks after therapy), one patient showed a complete response, one showed a partial response (PR) and five had disease stabilization (SD). Five patients were given up to three repeated Tenarad treatments. One patient showed SD which then improved to a PR, three showed clinical benefit while maintaining SD and one patient showed disease progression. CONCLUSION: Tenarad RIT is effective in chemorefractory HL and resulted in objective responses or clinical benefit in the majority of patients. Toxicity was acceptable despite the high load of prior treatments, previous ASCT and multiple Tenarad administrations. Further studies are planned to define the most effective schedule for this type of RIT in HL patients.

Abundant in vitro expression of the oncofetal ED-B-containing fibronectin translates into selective pharmacodelivery of (131)I-L19SIP in a prostate cancer patient.

PURPOSE: The extradomain B of fibronectin (ED-B) is a promising vascular target for selective pharmacodelivery in cancer patients. We analyzed a large series of prostatectomies from patients with prostate cancer, hyperplastic prostate disease, and normal prostates to study extent and tumor-selectivity of ED-B expression. METHODS: Using immunohistology, 68 adenocarcinomas of the prostate or prostate cancer-inflicted lymph nodes, 4 samples of benign prostatic hyperplasia, and 6 normal prostate glands were studied for ED-B expressing newly formed blood vessels. Further, we treated an advanced prostate cancer patient with the anti-ED-B antibody (131)I-L19SIP to study in vivo target accessibility. RESULTS: ED-B-positive blood vessels were found significantly more frequent in prostate cancers as compared with peritumoral prostate tissues or normal prostate glands, independent of tumor differentiation. The ED-B-positive blood vessels' density was 97 (±23), 65 (±9), and 59 (±9)/mm(2) in G3, G2, and G1 prostate cancers, respectively, and 7 (±5)/mm(2) in normal prostate glands. In high-grade (G3) prostate cancers, also the peritumoral tissue showed a higher density of ED-B vessels than normal prostate glands. Similar results were obtained when ED-B-positive vessel density was expressed as a fraction of CD34-positive vessel density. Finally, selective uptake of ED-B-binding (131)I-L19SIP to tumor lesions was found in an advanced prostate cancer patient by whole-body planar scintigraphy. CONCLUSIONS: ED-B-positive blood vessels were found to a large extent in prostate cancer tissues, but only rarely in normal prostates or benign prostatic hyperplasia. Whole-body planar scintigraphy in a prostate cancer patient confirmed selective uptake of (131)I-L19SIP in the prostate cancer tissues, qualifying ED-B as a promising target for selective pharmacodelivery of anticancer agents in prostate cancer.

Antibody-based delivery of interleukin-2 to neovasculature has potent activity against acute myeloid leukemia.

Acute myeloid leukemia (AML) is a rapidly progressing disease that is accompanied by a strong increase in microvessel density in the bone marrow. This observation prompted us to stain biopsies of AML and acute lymphoid leukemia (ALL) patients with the clinical-stage human monoclonal antibodies F8, L19, and F16 directed against markers of tumor angiogenesis. The analysis revealed that the F8 and F16 antibodies strongly stained 70% of AML and 75% of ALL bone marrow specimens, whereas chloroma biopsies were stained with all three antibodies. Therapy experiments performed in immunocompromised mice bearing human NB4 leukemia with the immunocytokine F8-IL2 [consisting of the F8 antibody fused to human interleukin-2 (IL-2)] mediated a strong inhibition of AML progression. This effect was potentiated by the addition of cytarabine, promoting complete responses in 40% of treated animals. Experiments performed in immunocompetent mice bearing C1498 murine leukemia revealed long-lasting complete tumor eradication in all treated mice. The therapeutic effect of F8-IL2 was mediated by both natural killer cells and CD8(+) T cells, whereas CD4(+) T cells appeared to be dispensable, as determined in immunodepletion experiments. The treatment of an AML patient with disseminated extramedullary AML manifestations with F16-IL2 (consisting of the F16 antibody fused to human IL-2, currently being tested in phase 2 clinical trials in patients with solid tumors) and low-dose cytarabine showed significant reduction of AML lesions and underlines the translational potential of vascular tumor-targeting antibody-cytokine fusions for the treatment of patients with leukemia.

Phase 0 microdosing PET study using the human mini antibody F16SIP in head and neck cancer patients.

UNLABELLED: The aim of this microdosing phase 0 clinical study was to obtain initial information about pharmacokinetics, biodistribution, and specific tumor targeting of the antitenascin-C mini antibody F16SIP. METHODS: Two milligrams of F16SIP, labeled with 74 MBq of (124)I, were intravenously administered to patients with head and neck cancer (n = 4) scheduled for surgery 5-7 d later. Immuno-PET scans were acquired at 30 min and 24 h after injection. For pharmacokinetic analysis, blood samples were taken at different time points after infusion. Tissue uptake was extracted from whole-body PET scans. In addition, ex vivo radioactivity measurements of blood and of biopsies from the surgical specimens were performed. RESULTS: (124)I-F16SIP was well tolerated. Uptake was visible mainly in the liver, spleen, kidneys, and bone marrow and diminished over time. Tumor uptake increased over time, with all 4 tumors visible on 24-h PET images. The tumor-to-blood ratio was 7.7 ± 1.7 at the time of surgery. Pharmacokinetic analysis revealed good bioavailability of (124)I-F16SIP. CONCLUSION: Performing a microdosing immuno-PET study appeared feasible and demonstrated adequate bioavailability and selective tumor targeting of (124)I-F16SIP.The results of this study justify further clinical exploration of (124)I-F16SIP-based therapies.

Isolated limb perfusion with the tumor-targeting human monoclonal antibody-cytokine fusion protein L19-TNF plus melphalan and mild hyperthermia in patients with locally advanced extremity melanoma.

BACKGROUND: L19-TNF is a tumor-targeting immunocytokine composed of the human L19 antibody binding to extra domain B (ED-B) of fibronectin of newly formed blood vessels, and of human TNF. This exploratory trial evaluates safety and clinical activity of L19-TNF plus melphalan-containing isolated limb perfusion (ILP) in extremity melanoma patients. METHODS: Seven and 10 patients received 325 µg and 650 µg of L19-TNF, respectively, during the ILP. Patients were studied for safety, tolerability, and clinical activity of this experimental L19-TNF ILP procedure. RESULTS: Non-hematologic toxicity of L19-TNF ILP was very low, but severe myelosuppression was seen in four patients. Although L19-TNF was administered at a TNF-equivalent dose of only 3.13 and 6.25% of the approved TNF (Beromun®) dose of 4 mg, L19-TNF ILP induced objective responses in 86 and 89% of patients, respectively, including a complete response (CR) in 5/10 patients treated with L19-TNF ILP at 650 µg that was durable at 12 months in four patients. No CR was seen at 325 µg of L19-TNF. CONCLUSIONS: ILP with L19-TNF had a favorable safety and a promising activity profile at a dose of 650 µg of L19-TNF, supporting the exploration of higher L19-TNF doses and a Phase II trial comparing L19-TNF ILP with standard melphalan-containing ILP.

Radretumab radioimmunotherapy in patients with brain metastasis: a 124I-L19SIP dosimetric PET study.

Radioimmunotherapy (RIT) with (131)I-labeled L19SIP (radretumab; a small immunoprotein format antibody directed against the ED-B domain of fibronectin; ∼ 80 kDa molecular weight) has been investigated in several clinical trials. Here, we describe the use of immuno-PET imaging with iodine-124 ((124)I)-labeled L19SIP to predict doses delivered to tumor lesions and healthy organs by a subsequent radretumab RIT in patients with brain metastases from solid cancer. Bone marrow doses were evaluated both during the diagnostic phase and posttherapy, measuring activities in blood (germanium detector) and whole body (lanthanum bromide detector). Expected doses for radretumab administration (4,107 MBq/m(2)) were calculated from data obtained after administration of an average of 167 MBq (124)I-L19SIP to 6 patients. To assess lesion average doses, the positron emission tomography (PET) scanner was calibrated for the use of (124)I with an International Electrotechnical Commission (IEC) Body Phantom and recovery coefficients were calculated. The average dose to bone red marrow was 0.21 Gy/GBq, with high correlation between provisional and actual posttherapy doses. Although the fraction of injected activity in normal organs was similar in different patients, the antibody uptake in the neoplastic lesions varied by as much as a factor of 60. Immuno-PET with (124)I-labeled L19SIP offers significant advantages over conventional (131)I imaging, in particular accuracy of dosimetric results. Furthermore, the study indicates that antibody uptake can be highly variable even in different lesions of the same patient and that immuno-PET procedures may guide product development with armed antibodies.

Radioimmunotherapy with radretumab in patients with relapsed hematologic malignancies.

UNLABELLED: We present here a systematic analysis of lymphoma and MM patients recruited into 2 clinical trials or treated with radretumab according to compassionate use, describing the biodistribution, dosimetry, safety, and clinical activity of radretumab. METHODS: Uptake in lymphoma lesions, safety, and clinical activity of radretumab radioimmunotherapy (R-RIT) were evaluated in 18 relapsed lymphoma or multiple myeloma patients. RESULTS: In 14 of 18 patients, selective tumor uptake was found; 11 of 15 lymphoma patients, including 9 of 11 with Hodgkin lymphoma (HL), were eligible for R-RIT (a priori criteria-based target-to-bone marrow ratio > 10:1 for EudraCT no. 2005-000545 or > 4:1 for EudraCT no. 2007-007241-12 at dosimetric imaging). Two HL and 1 diffuse large B cell lymphoma patient achieved complete response; 1 HL patient had partial response. Both multiple myeloma patients receiving R-RIT experienced stabilization of disease. Therefore, the overall objective response rate was 40%. Uncomplicated grade 3-4 thrombocytopenia or leukocytopenia was observed in 5 R-RIT patients, lasting 4-129 d. CONCLUSION: R-RIT showed a favorable benefit and risk profile in advanced relapsed lymphoma patients and induced complete response in 2 heavily pretreated, relapsed HL patients and in 1 diffuse large B cell lymphoma patient. These results warrant further exploration of R-RIT in larger phase II clinical trials.

A dose-escalation and signal-generating study of the immunocytokine L19-IL2 in combination with dacarbazine for the therapy of patients with metastatic melanoma.

PURPOSE: L19-IL2 is an immunocytokine composed of an antibody fragment specific to the EDB domain of fibronectin, a tumor angiogenesis marker, and of human interleukin-2 (IL2). L19-IL2 delivers IL2 to the tumor site exploiting the selective expression of EDB on newly formed blood vessels. Previously, the recommended dose of L19-IL2 monotherapy was defined as 22.5 million international units (Mio IU) IL2 equivalents. In this study, safety and clinical activity of L19-IL2 in combination with dacarbazine were assessed in patients with metastatic melanoma. EXPERIMENTAL DESIGN: The first 10 studied patients received escalating doses of L19-IL2 on days 1, 3, and 5 in combination with 1 g/m(2) of dacarbazine on day 1 of a 3-weekly therapy cycle. Subsequently, 22 patients received L19-IL2 at recommended dose plus dacarbazine. Up to six treatment cycles were given, followed by a maintenance regimen with biweekly L19-IL2. RESULTS: The recommended dose of L19-IL2 in combination with dacarbazine was defined as 22.5 Mio IU. Toxicity was manageable and reversible, with no treatment-related deaths. Twenty-nine patients were evaluable for efficacy according to Response Evaluation Criteria in Solid Tumors (RECIST). In a centralized radiology analysis, eight of 29 (28%) patients achieved a RECIST-confirmed objective response, including a complete response still ongoing 21 months after treatment beginning. The 12-month survival rate and median overall survival of the recommended dose-treated patients (n = 26) were 61.5% and 14.1 months, respectively. CONCLUSIONS: The repeated administration of L19-IL2 in combination with dacarbazine is safe and shows encouraging signs of clinical activity in patients with metastatic melanoma. This combination therapy is currently evaluated in a randomized phase II trial with patients with metastatic melanoma.

The tumour-targeting human L19-IL2 immunocytokine: preclinical safety studies, phase I clinical trial in patients with solid tumours and expansion into patients with advanced renal cell carcinoma.

BACKGROUND: L19-IL2, a tumour-targeting immunocytokine composed of the recombinant human antibody fragment L19 (specific to the alternatively-spliced EDB domain of fibronectin, a well characterised marker of tumour neo-vasculature) and of human IL2, has demonstrated strong therapeutic activity in animal cancer models. This phase I/II trial was performed to evaluate safety, tolerability, recommended phase II dose (RD) and early signs of activity of L19-IL2. PATIENTS AND METHODS: Five cohorts of patients with progressive solid tumours (n=21) received an intravenous infusion of L19-IL2 (from 5 to 30 Mio IU IL2 equivalent dose) on days 1, 3 and 5 every 3 weeks. This treatment cycle was repeated up to six times. In the following expansion phase, patients with metastatic renal cell carcinoma (RCC) (n=12) were treated at the RD of L19-IL2. Clinical data and laboratory findings were analysed for safety, tolerability and activity. RESULTS: Preclinical studies in rats and monkeys did not raise any safety concerns. The RD was defined to be 22.5 Mio IU IL2 equivalent. Pharmacokinetics of L19-IL2 was dose proportional over the tested range, with a terminal half-life of 2-3h. Toxicities were manageable and reversible with no treatment-related deaths. We observed stable disease in 17/33 patients (51%) and 15/18 with mRCC (83%) after two cycles. Median progression-free survival of RCC patients in the expansion phase of the study was 8 months (1.5-30.5). CONCLUSIONS: L19-IL2 can be safely and repeatedly administered at the RD of 22.5 Mio IU IL2 equivalent in advanced solid tumours. Preliminary evaluation suggests clinical activity of L19-IL2 in patients with mRCC.

Expression, engineering and characterization of the tumor-targeting heterodimeric immunocytokine F8-IL12.

Proinflammatory cytokines have been used for several years in patients with advanced cancer but their administration is typically associated with severe toxicity hampering their application to therapeutically active regimens. This problem can be overcome by using immunocytokines (cytokines fused to antibody or antibody fragments) which selectively deliver the active cytokine to the tumor environment. Preclinical and recent clinical results confirmed that this approach is a very promising avenue to go. We designed an immunocytokine consisting of the scFv(F8) specific to extra-domain A of fibronectin and the very potent human cytokine interleukin-12 (IL12). The heterodimeric nature of IL12 allows the engineering of various immunocytokine formats, based on different combinations of the two subunits (p35 and p40) together with the scFv. In comparison to monomeric or homodimeric cytokines, the construction of a heterodimeric immunocytokine poses many challenges, e.g. gene dosing, stable high-yield expression as well as good manufacture practice (GMP) purification and characterization. In this paper, we describe the successful construction, characterization and production of the heterodimeric immunocytokine F8-IL12. The positive outcome of this feasibility study leads now to GMP production of F8-IL12, which will soon enter clinical trials.

Expression of the oncofetal ED-B-containing fibronectin isoform in hematologic tumors enables ED-B-targeted 131I-L19SIP radioimmunotherapy in Hodgkin lymphoma patients.

Current treatment of hematologic malignancies involves rather unspecific chemotherapy, frequently resulting in severe adverse events. Thus, modern clinical research focuses on compounds able to discriminate malignant from normal tissues. Being expressed in newly formed blood vessels of solid cancers but not in normal mature tissues, the extradomain B of fibronectin (ED-B FN) is a promising target for selective cancer therapies. Using immunohistology with a new epitope retrieval technique for paraffin-embedded tissues, ED-B FN expression was found in biopsies from more than 200 Hodgkin and non-Hodgkin lymphoma patients of nearly all entities, and in patients with myeloproliferative diseases. ED-B FN expression was nearly absent in normal lymph nodes (n = 10) and bone marrow biopsies (n = 9). The extent of vascular ED-B FN expression in lymphoma tissues was positively correlated with grade of malignancy. ED-B FN expression was enhanced in lymph nodes with severe lymphadenopathy and in some hyperplastic tonsils. The in vivo accessibility of ED-B FN was confirmed in 3 lymphoma patients, in whom the lymphoma lesions were visualized on scintigraphy with (131)I-labeled L19 small immunoprotein ((131)I-L19SIP). In 2 relapsed Hodgkin lymphoma patients(131)I-L19SIP radioimmunotherapy induced a sustained partial response, qualifying ED-B FN as a promising target for antibody-based lymphoma therapies.

A general method for the selection of high-level scFv and IgG antibody expression by stably transfected mammalian cells.

The isolation of mammalian cell lines capable of high-yield expression of recombinant antibodies is typically performed by screening multiple individual clones by limiting dilution techniques. A number of experimental strategies have recently been devised to identify high-expressing clones, but protocols are often difficult to implement, time consuming, costly and limited in terms of number of clones which can be screened. In this article, we describe new vectors for the expression of recombinant antibodies in IgG format and in other formats, based on the single-chain Fv module, as well as a high-throughput screening procedure, based on the direct staining of antibodies transiting the membrane of a stably transfected cell, followed by preparative sorting using a high-speed cell sorter. This procedure allows, in one step, to deposit single cells into individual wells of a 96-well microtiter plate (thus facilitating cloning) and to preferentially recover those rare cell populations which express dramatically higher levels of recombinant antibody. Using cell cultures followed by affinity purification techniques, we could confirm that the new vectors and the new screening procedure reliably yield high-expression clones and homogenous protein preparations. We expect that these techniques should find broad applicability for both academic and industrial antibody engineering research.

Antibody-mediated delivery of interleukin-2 to the stroma of breast cancer strongly enhances the potency of chemotherapy.

PURPOSE: There is an interest in the discovery of biopharmaceuticals, which are well tolerated and which potentiate the action of anthracyclines and taxanes in breast cancer therapy. EXPERIMENTAL DESIGN: We have produced a recombinant fusion protein, composed of the human antibody fragment scFv(F16) fused to human interleukin-2 (F16-IL2), and tested its therapeutic performance in the MDA-MB-231 xenograft model of human breast cancer. The F16 antibody is specific to the alternatively spliced A1 domain of tenascin-C, which is virtually undetectable in normal tissues but is strongly expressed in the neovasculature and stroma of breast cancer. RESULTS: When used as monotherapy, F16-IL2 displayed a strikingly superior therapeutic benefit compared with unconjugated recombinant IL-2. The administration of doxorubicin either before (8 days, 24 h, or 2 h) or simultaneously with the injection of F16-IL2 did not decrease the accumulation of immunocytokine in the tumor as measured by quantitative biodistribution analysis. Therapy experiments, featuring five once per week coadministrations of 20 mug F16-IL2 and doxorubicin, showed a statistically significant reduction of tumor growth rate and prolongation of survival at a 4 mg/kg doxorubicin dose but not at a 1 mg/kg dose. By contrast, combination of F16-IL2 with paclitaxel (5 and 1 mg/kg) exhibited a significant therapeutic benefit compared with paclitaxel alone at both dose levels. F16-IL2, alone or in combination with doxorubicin, was well tolerated in cynomolgus monkeys at doses equivalent to the ones now used in clinical studies. CONCLUSIONS: F16-IL2 may represent a new useful biopharmaceutical for the treatment of breast cancer.

Immunoscintigraphic detection of the ED-B domain of fibronectin, a marker of angiogenesis, in patients with cancer.

PURPOSE: ED-B fibronectin is expressed only during angiogenic processes and in tissues undergoing growth and/or extensive remodeling. We demonstrated previously the possibility to target and selectively deliver therapeutic substances to tumor vasculature in experimental animal models using a human recombinant antibody fragment, L19, specific for the ED-B domain of fibronectin. Here we evaluate the possibility of targeting primary tumors and metastatic lesions in cancer patients through immunoscintigraphy using (123)I-labeled dimeric L19 [L19(scFv)(2)]. EXPERIMENTAL DESIGN: Twenty patients (34-79 years of age) with lung, colorectal, or brain cancer, whose tumors had been confirmed by imaging techniques and/or histologically, were admitted to the immunoscintigraphic investigation. RESULTS: The dimeric L19 antibody selectively localized in tumor lesions in aggressive types of lung cancer and colorectal cancer. Because ED-B fibronectin is expressed only during angiogenic processes and in tissues undergoing growth and/or extensive remodeling, L19(scFv)(2) is able to distinguish between quiescent and actively growing lesions. No side effects were observed. CONCLUSIONS: The ability of L19(scFv)(2) to target tumors in patients provides the foundations for new therapeutic applications, in which the L19 antibody is engineered to selectively deliver bioactive molecules to primary tumors as well as to metastases.