Use of Thrombopoietin in Combination with Chemotherapy and Granulocyte Colony-Stimulating Factor for Peripheral Blood Progenitor Cell Mobilization

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James L. Gajewski,1 Gabriela Rondon,1 Michele L. Donato,1 Paolo Anderlini,1 Martin Korbling,1 Cindy Ippoliti,1 Mark Benyunes,2 Langdon L. Miller,3 Denise LaTemple,4 Denny Jones,2 Mark Ashby,2 Sue Hellmann,2 April Durett,1 Jo Lauppe,1 Deborah Geisler,1 Issa F. Khouri,1 Sergio A. Giralt,1 Borje Andersson,1 Naoto T. Ueno,1 Richard Champlin1

1University of Texas M. D. Anderson Cancer Center, Department of Blood and Marrow Transplantation, Houston, Texas; 2Genentech Inc, South San Francisco, California; 3Pharmacia Corporation, Peapack, New Jersey; 4Ingenix Pharmaceutical Services, Parsippany, New Jersey

Correspondence and reprint requests: James L. Gajewski, MD, Department of Blood and Marrow Transplantation, M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Box 423, Houston, TX 77030-4095 (e-mail: [email protected]).

Received March 13, 2002; accepted July 16, 2002

ABSTRACT This phase I/II dose-escalation study examined the safety and efficacy of recombinant human thrombopoietin (rhTPO) and granulocyte colony-stimulating factor (G-CSF) for postchemotherapy mobilization of peripheral blood progenitor cells (PBPCs) in patients with advanced breast cancer. Patients received cyclophosphamide, etoposide, and cisplatin (CVP) followed by G-CSF (6 µg/kg twice a day) and rhTPO (0.6, 1.2, 2.4, or 3.6 µg/kg as a single dose on day 5 or as 3 doses on days 5, 7, and 9 after chemotherapy). PBPCs were collected by daily leukapheresis when the postnadir white blood cell count reached ≥2 × 109/L; leukapheresis was continued until acquisition of a target dose of ≥5 × 106 CD34+ cells/kg. Mobilized PBPCs were transplanted into patients after additional high-dose chemotherapy with cyclophosphamide, carmustine, and thiotepa (CBT). Comparisons were made with contempora- neously treated, nonrandomized, control patients who received the same chemotherapy regimens and G-CSF support but who did not receive rhTPO. Of 32 evaluable patients receiving rhTPO and G-CSF after CVP, 91% required only 1 leukapheresis to achieve a target PBPC graft; by contrast, only 69% of 36 of the control patients achieved the target graft with just 1 leukapheresis (P = .026). A median of 26.7 × 106 CD34+ cells/kg per leukapheresis was obtained from the rhTPO-treated patients compared with 11.5 × 106 cells/kg per leukapheresis from the controls (P = .09). Higher rhTPO doses appeared to yield more CD34+ cells. When PBPCs were infused after high- dose CBT chemotherapy, the median times to return of an absolute neutrophil count of 0.5 × 109/L and a platelet count of 20 × 109/L were 15 and 16 days, respectively; these values did not differ from those in the control group (15 days for both neutrophil and platelets). No patient developed anti-TPO antibodies. These results indicate that rhTPO safely and effectively augments the number of PBPCs mobilized with chemotherapy and G-CSF and can reduce the required number of leukaphereses. Further studies are also warranted in patients who are likely to expe- rience suboptimal PBPC mobilization when treated with currently available techniques.

KEY WORDS Leukapheresis • Thrombopoiesis • Recombinant human thrombopoietin • Breast cancer • Autologous hematopoietic progenitor cell transplants

INTRODUCTION cies [1-6]. Recombinant hematopoietic growth factors, Peripheral blood progenitor cell (PBPC) transplantation including granulocyte colony-stimulating factor (G-CSF) has made possible the widespread use of myeloablative cyto- and granulocyte-macrophage (GM)-CSF, have been used toxic therapy to treat chemotherapy-responsive malignan- alone or with chemotherapy to mobilize PBPCs that can be

550 rhTPO for PBPC Mobilization harvested by leukapheresis [7-9]. From 2 to 6 leukapheresis Patients were excluded from the study if they had mor- sessions are often required to obtain a sufficient number of phologically identified bone marrow involvement with malig- PBPCs (usually ≥2 × 106 CD34+ cells/kg) for rapid and nancy, central nervous system metastases, a history of platelet durable hematopoietic recovery [9]. In some patients, disorders, venous thromboembolism, or myocardial or central PBPCs are difficult to mobilize, particularly in patients who nervous system ischemia within 6 months before study entry. have been heavily pretreated with chemotherapy or who Patients could not have received more than 3 prior chemo- have had prior radiation therapy to marrow-bearing sites therapy regimens. Patients were also excluded from study [9]. Collection of an insufficient number of CD34+ hemato- participation if they had undergone prior treatment with mit- poietic progenitors may render these patients ineligible for omycin C or carmustine (BCNU), previous pelvic irradiation, high-dose chemotherapies requiring progenitor cell sup- prior bone marrow or PBPC transplantation, or treatment port. More effective treatment to mobilize hematopoietic with chemotherapy or experimental drugs ≤4 weeks before stem/progenitor cells is needed to reduce collection times study entry. and enhance cell yields. To enhance the understanding of the influence of Thrombopoietin (TPO), the ligand for the cytokine rhTPO on PBPC mobilization efficacy and posttransplanta- receptor c-mpl, is a naturally occurring glycosylated peptide tion hematologic recovery that could be gained by this growth factor and the primary regulator of thrombopoiesis study, we identified a control group. The control group [10-15]. Activation of c-mpl by TPO stimulates the differ- comprised patients with stage II to III breast cancer who entiation of megakaryocyte progenitors, promotes mega- were concurrently and identically treated on an institutional karyocyte proliferation and maturation, and increases protocol but who did not receive rhTPO. The rhTPO study platelet production. TPO also acts synergistically with other was episodically closed to patient accrual to allow time to hematopoietic growth factors to enhance the differentiation observe for toxicity endpoints. We had a trial running con- of primitive hematopoietic cells committed to the erythroid currently so that all potential study patients were treated on and myelomonocytic lineages [16]. Recombinant human protocol. This study was opened 1 year prior to the rhTPO thrombopoietin (rhTPO), a full-length glycosylated mole- study and was closed in 2002. The patients in the control cule, is homologous to native TPO. In preclinical studies, study were treated within 2 years of the rhTPO trial to administration of TPO to normal mice caused a rapid 4- to allow for similarities in supportive care. Flow cytometry 6-fold increase in circulating platelets and increased the analyses in these patients were performed by the same labo- number and ploidy of bone marrow and splenic megakaryo- ratory using the same gating as was employed in rhTPO- cytes [12]. In murine models of myelosuppression, TPO treated patients. accelerated platelet recovery and ameliorated thrombocy- All patients (including those treated in the control topenia [17]. Similar results were noted in the first human group) were required to sign a written informed consent trials in cancer patients; when administered alone or with document that had been approved by the institutional myelosuppressive and myeloablative cytotoxic chemo- review board. therapy, rhTPO safely stimulated thrombopoiesis [18-21], and when administered with G-CSF or GM-CSF, rhTPO Study Treatment enhanced PBPC mobilization [21,22]. During the mobilization phase, patients received PBPC mobilization can be enhanced when colony- cyclophosphamide, etoposide, and cisplatin (CVP) chemo- stimulating factors are administered after myelosuppressive therapy. The regimen comprised a single cycle of intra- chemotherapy [9]; however, it has not been previously venous treatment with cyclophosphamide 1.5 g/m2 on days demonstrated that addition of rhTPO to a regimen of 1 to 3, etoposide 250 mg/m2 on days 1 to 4, and cisplatin chemotherapy and G-CSF can improve mobilization effi- 40 mg/m2 on days 1 to 3 [23]. As outlined in Table 1, cohorts ciency. This study was conducted to evaluate the safety and of 3 to 6 patients were sequentially assigned to receive pro- PBPC-mobilizing activity of single and multiple doses of gressively longer courses and higher doses of rhTPO (Phar- rhTPO combined with G-CSF in patients with breast cancer macia, Peapack, NJ; Genentech, South San Francisco, CA) who were receiving chemotherapy for PBPC mobilization. by intravenous injection via central venous catheter. Patients assigned to group A of the study received a single dose of rhTPO at dose levels of 0.6, 1.2, 2.4, or 3.6 µg/kg on day 5 PATIENTS AND METHODS after CVP. Patients in group B were treated with rhTPO at Patients dose levels of 0.6, 1.2, 2.4, or 3.6 µg/kg on days 5, 7, and 9 Patients with a histologically confirmed diagnosis of after CVP. Patients in group C received 1.2 µg/kg of high-risk stage II/III or metastatic breast cancer were rhTPO on days 5, 7, and 9 after CVP and on days –14, –11, enrolled in the study. Patients with metastatic disease were 0, 2, 4, and 6 relative to high-dose chemotherapy and PBPC required to have evidence that their cancer had responded infusion during the transplantation phase of the study. No to standard-dose chemotherapy and to have minimal resid- intrasubject dose escalation was allowed. In all groups, the ual disease. Patients were also required to have an Eastern maximum tolerated rhTPO dose was defined as 1 dose level Cooperative Oncology Group performance status of 0 or 1, below that associated with 2 episodes of grade 3 toxicity or white blood cell count (WBC) ≥3.5 × 109/L, absolute neu- an increase in platelet count to >600 × 109/L persisting trophil count (ANC) ≥1.5 × 109/L, platelet count ≥100 × beyond 24 hours. G-CSF (Neupogen; Amgen, Thousand 109/L and ≤500 × 109/L, adequate liver function, left ven- Oaks, CA) 6 µg/kg was administered to all patients twice tricular cardiac ejection fraction ≥50%, and creatinine clear- daily (subcutaneously or intravenously) starting on day 5 ance ≥60 mL/min. after CVP chemotherapy and continuing until completion

BB&MT 551 J. L. Gajewski et al.

Table 1. Baseline Patient Characteristics

rhTPO-Treated Patients

Group A* Group B† Group C‡ Control rhTPO dose level, µg/kg 0.6 1.2 2.4 3.6 0.6 1.2 2.4 3.6 1.2 Overall Patients

Enrolled, n 4 3 3 3 5 3 3 3 6 33 37 Treated, n 4 3 3 3 5 3 3 3 6 33 37 Evaluable, n After CVP 3 3 3 3 5 3 3 3 6 32 36 After CBT 3 3 3 3 5 3 3 3 6 32 35 Age at transplantation, 44 45 48 48 43 51 32 45 49.5 46 47 median (range), y (28-46) (39-51) (40-49) (45-55) (36-50) (28-55) (30-48) (36-46) (36-54) (28-55) (27-62) Time since diagnosis, 5.2 5.9 6.9 5.9 9.2 10.2 7.4 24.1 21.8 7.5 7.1 median (range), mo (5.2-6.4) (5.6-6.1) (3.9-7.3) (4.8-64.2) (5.4-11.0) (7.6-56.3) (5.1-7.8) (10.1-95.1) (7.0-53.4) (3.9-95.1) (4.0-14.3) Disease stage, n II 1 1 1 1 2 1 1 0 1 9 17 III 3 2 2 1 2 1 1 1 0 13 20 Metastatic 0 0 0 1 1 1 1 2 5 11 0

*Group A patients received rhTPO on day 5 following CVP chemotherapy. †Group B patients received rhTPO on days 5, 7, and 9 following CVP chemotherapy. ‡Group C patients received rhTPO on days 5, 7, and 9 following CVP chemotherapy and on days –14, –11, 0, 2, 4, and 6 relative to CBT chemotherapy and PBPC transplantation. of leukapheresis. Patients were not to receive aspirin (except Anti-TPO Antibody Screening when used to treat thrombosis), nonsteroidal antiinflamma- Blood samples were serially tested for the presence of tory agents, anticoagulants, or colony-stimulating factors anti-TPO antibodies at the screening visit, before the first other than G-CSF. rhTPO administration, and weekly through day 49 of the Patients underwent large-volume leukapheresis (3 times follow-up period. Initial screening was performed using an their calculated total blood volume) for PBPC collection enzyme-linked immunosorbent assay (ELISA) based on the after the CVP nadir when the WBC reached ≥2 × 109/L. full-length TPO molecule. The assay reported results as PBPCs were collected daily for up to 5 days or until a target either positive or negative. For samples identified as positive cell dose of 5 × 106 CD34+ cells/kg was obtained. Pro- in the full length ELISA, the sample was titered in a similar grammed freezing was used to cryopreserve cells in 10% assay based on a truncated version of the molecule that dimethylsulfoxide. Patients with a minimum cumulative tar- included the c-mpl binding domain. Such samples were also get dose of ≥2.0 × 106 CD34+ cells/kg were eligible to pro- evaluated in functional assays to determine if any potential ceed to the transplantation phase of the study. antibodies blocked TPO binding to the c-mpl receptor and During the transplantation phase, patients received high- inhibited proliferation of the TPO-dependent HU-3 cell dose intravenous chemotherapy consisting of cyclophos- line. For antibodies to be considered neutralizing, a positive phamide 2 g/m2, BCNU 150 mg/m2, and thiotepa 240 mg/m2 HU-3 bioassay result in the presence of persistent, clinically (CBT); all drugs were given on days –7, –6, and –5. PBPCs significant thrombocytopenia was required. were infused 5 days after completion of CBT chemotherapy (on day 0) [23]. G-CSF 5 µg/kg was administered (either Statistical Analysis intravenously or subcutaneously) to patients in all study Patient characteristics, treatment administration, and groups daily starting 1 day after PBPC infusion and contin- potential rhTPO-related adverse events were assessed uing until ANC recovery to ≥5 × 109/L. Only patients in descriptively. The t test was used to compare the total group C received rhTPO 1.2 µg/kg on days –14, –11, 0, 2, number of CD34+ PBPCs mobilized in rhTPO-treated 4, and 6 relative to CBT therapy and PBPC infusion. patients and controls. The Wilcoxon signed-rank test was Platelet transfusions were administered to all patients with similarly employed to assess the number of leukaphereses platelet counts of ≤20 × 109/L. required to obtain the target CD34+ cell dose. The number of days required to reach an ANC >0.5 × 109/L and Clinical Patient Monitoring platelet counts ≥20, 50, and 100 × 109/L were calculated. Patients were monitored for adverse reactions after each Time from start of CVP therapy was calculated in the injection of rhTPO and at each visit. Total WBC, WBC dif- mobilization phase, and time from PBPC infusion (day 0) ferential, and platelet counts were determined on the days of was determined in the transplantation phase. Kaplan- rhTPO and G-CSF administration and before each leuka- Meier methods and the Tarone-Ware log-rank test were pheresis. Blood counts were monitored daily in the trans- used to compare time to hematologic recovery for all plantation phase. The serum chemistry profile, electrolyte rhTPO-treated patients and controls. The numbers of values, and coagulation parameters were monitored weekly platelet transfusions required were also tabulated. Statisti- during the mobilization, transplantation, and follow-up cal software Systat 8.0 (SPSS, Chicago, IL) was used for phases (on days 28, 35, 42, and 49). statistical analysis.

552 rhTPO for PBPC Mobilization

Table 2. Leukapheresis and PBPC Harvest*

rhTPO-Treated Patients Control Group A Group B Group C Overall Patients P Evaluable, n 3 3 3 3 5 3 3 3 6 32 36 rhTPO dose level, 0.6 1.2 2.4 3.6 0.6 1.2 2.4 3.6 1.2 — — µg/kg Cumulative rhTPO 0.6 1.2 2.4 3.6 1.8 3.6 7.2 10.8 3.6 — — dose, µg/kg

No. leukaphereses 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 ND to collect target (1.0-1.0) (1.0-2.0) (1.0-2.0) (1.0-1.0) (1.0-2.0) (1.0-1.0) (1.0-1.0) (1.0-1.0) (1.0-1.0) (1.0-2.0) (1.0-3.0) graft, median (range) Patients with target 3 2 2 3 4 3 3 3 6 29 25 .026 graft after 1 leuk- (100) (67) (67) (100) (80) (100) (100) (100) (100) (91) (69) apheresis, n (%) No. of CD34+ cells/kg 28.4 24.1 15.7 7.5 9.4 58.0 89.1 135.1 38.4 26.7 11.5 .09 per leukapheresis, (18.5-42.8) (15.4-24.9)(4.5-182.3) (7.4-62.6) (4.8-21.0) (32.4-85.4) (4.3-102.2)(123.3-198.0) (3.7-82.2) (3.7-198.0) (1.4-141.3) median (range), ×106

*P values are for comparison of rhTPO-treated groups overall (n = 32) with controls (n = 36). See Table 1 footnotes for descriptions of patient groups. ND indicates not determined.

RESULTS (72%). After CBT administration, the most common adverse Patient Characteristics events were esophagitis (87%), diarrhea (84%), fever (81%), A total of 33 patients were enrolled in the rhTPO treat- hypokalemia (74%), and nausea (74%). No differences in the ment groups. All 33 rhTPO-treated patients were evaluable incidence, severity, or type of chemotherapy-related adverse for treatment safety during the mobilization phase. One events were observed among the rhTPO regimens. patient in group A developed chemotherapy-related pul- During the mobilization phase, 5 patients experienced monary toxicity after receiving CVP and did not undergo adverse effects that were described as possibly related to leukapheresis or transplantation; the other 32 rhTPO- rhTPO. These events included catheter thromboses (n = 2), treated patients were evaluable during the transplantation bone pain (n = 1), rash (n = 1), and anxiety (n = 1). During phase. The control group comprised 37 patients. One the transplantation phase, in which only patients in group C patient in this group did not undergo leukapheresis; the received rhTPO, events considered possibly related to other 36 patients were evaluable for PBPC mobilization rhTPO included fever (n = 4), rash (n = 2), and chills (n = 1). endpoints. One of these 36 patients did not undergo CBT None of the adverse events that were possibly linked to treatment, so there were 35 evaluable control patients dur- rhTPO required discontinuation of rhTPO dosing. No ing the transplantation phase. maximum tolerated dose of rhTPO was reached over the Patient characteristics are described in Table 1. The dose range tested. median age of patients in the rhTPO-treated groups was relatively young at 46 years (range, 28-55 years). The median PBPC Mobilization time from diagnosis of breast cancer to transplantation was Of the evaluable rhTPO-treated patients, 29 (91%) of 32 7.5 months (range, 3.9-95.1 months). The greatest propor- achieved a target PBPC graft of 5 × 106 CD34+ cells/kg after tion of patients had stage III disease. No patient had received only 1 leukapheresis (Table 2); only 25 (69%) of 36 evaluable more than 2 prior chemotherapy regimens. The characteris- control patients (P = .026) were able to achieve a target graft tics of the patients in the control group were similar to those with just 1 leukapheresis. The median yield of CD34+ of the patients in the rhTPO-treated groups. cells/kg per leukapheresis was 26.7 × 106 (range, 3.7-198.0) for all rhTPO-treated patients compared with 11.5 × 106 Treatment Administration and Safety (range, 1.4-141.3) in the control group. Because of a substan- During the mobilization phase, 13 patients received a sin- tial degree of variability, the difference between these results gle dose of rhTPO (group A) and 20 patients received 3 doses was not statistically significant (P = .09). Although cohort of rhTPO (groups B and C). During the transplantation sizes were small, there was a suggestion of a dose-dependent phase, 6 patients (group C) received 6 additional doses of increase in the number of CD34+ cells in patients receiving rhTPO, 3 prior to infusion of the transplant graft and 3 after- multiple rhTPO injections (Table 2, group B). ward. A total of 104 doses of rhTPO were administered to all patients entered in this study. Hematologic Recovery The adverse events experienced by the rhTPO-treated Patients were monitored for the recovery of neutrophils patients after CVP and CBT were those expected with these (ANC levels of 0.5 × 109/L and 1.0 × 109/L) and platelets chemotherapeutic regimens. After CVP administration, the (levels of 20 × 109/L, 50 × 109/L, and 100 × 109/L) after the most common adverse events reported were nausea (100%), mobilizing CVP chemotherapy. The time to recovery of vomiting (91%), diarrhea (88%), fever (81%), and headaches neutrophils did not differ signiﬁcantly in the rhTPO-treated

BB&MT 553 J. L. Gajewski et al.

Table 3. Mobilization Phase: Hematologic Recovery after CVP Chemotherapy*

Control Patients Days rhTPO-Treated Patients Days to Recovery, Median (Range) to Recovery, Median Group A (n = 12) Group B (n = 14) Group C (n = 6) Overall (n = 32) (Range) (n = 37) P

ANC 0.5 × 109/L 15 (14-17) 14.5 (13-21) 15 (13-18) 15 (13-21) 15 (13-17) NS ANC 1.0 × 109/L 15 (14-18) 15 (13-22) 15 (13-18) 15 (13-22) 15 (13-19) NS Platelets 20 × 109/L 15 (12-19) 15.5 (11-21) 15 (12-19) 15 (11-21) 16 (11-24) NS Platelets 50 × 109/L 18.5 (15-25) 18.5 (14-25) 17.5 (16-22) 18 (14-25) 19 (13-34) NS Platelets 100 × 109/L 20 (18-32) 20.5 (16-32) 21.5 (19-25) 20.5 (16-32) 24 (17-34) .007

*P values are for comparison of rhTPO-treated groups overall (n = 32) with controls (n = 37). See Table 1 footnotes for descriptions of patient groups. NS indicates not significant. patients compared to the control group (Table 3). Time to Other than these 2 patients, no other patients were positive platelet recovery to 20 × 109/L and 50 × 109/L did not differ for anti-TPO antibodies. None of the patients had positive significantly between the rhTPO-treated and control results in the ELISA evaluating antibody formation against groups. Platelet recovery to 100 × 109/L was more rapid in the truncated form of TPO containing the receptor-binding the rhTPO-treated group (P = .007), occurring a median of region. Likewise, there was no indication of positivity in the 3.5 days sooner than in the control group. functional assays assessing c-mpl receptor blocking or inhi- There were no apparent differences between rhTPO- bition of HU-3 proliferation. There was also no evidence of treated patients and controls in hematologic recovery after thrombocytopenia attributable to TPO neutralization. high-dose CBT chemotherapy and autologous transplantation of the mobilized PBPCs (Table 4). DISCUSSION Anti-TPO Antibody Testing Hematopoietic progenitors circulate in low frequency in Two patients had positive results for the screening the peripheral blood, but their numbers are markedly ELISA assay testing for anti-TPO antibodies to full-length increased after chemotherapy and after treatment with the TPO. One patient had positive test results at baseline prior hematopoietic growth factors G-CSF or GM-CSF [9]. After to receiving TPO and had a platelet count of 155,000. After high-dose chemotherapy and autologous PBPC transplanta- receiving 1 dose of TPO, the other patient had a positive tion, hematopoietic recovery correlates with the number of result on what was to have been day –7 prior to receiving CD34+ cells infused [24]. The minimum number of pro- the preparative regimen. This patient did not go on to genitor cells needed for transplantation is not precisely receive the transplant because of the development of inter- defined, but most centers generally require at least 1 to 2 × stitial pneumonitis from CVP. Within 24 days of recovering 106/kg CD34+ cells. A target dose of 3 to 5 × 106 CD34+ from CVP, the patient’s platelet counts had exceeded 90,000, cells/kg has been recommended to aid in prompt, reliable and the confirmatory titers were negative. Subsequent test- hematopoietic recovery [9]. ing on both patients was negative and both patients remain G-CSF alone is commonly used to mobilize blood pro- alive with normal platelet counts at the time of this report. genitors for collection. Even at optimal doses and after 4 or

Table 4. Transplantation Phases: Hematologic Recovery after High-Dose CBT Chemotherapy and PBPC Transplantation*

rhTPO-Treated Patients Control Group A Group B Group C Overall Patients P Evaluable, n 3 3 3 3 5 3 3 3 6 32 35 rhTPO dose level, 0.6 1.2 2.4 3.6 0.6 1.2 2.4 3.6 1.2 — — µg/kg Cumulative rhTPO 0.6 1.2 2.4 3.6 1.8 3.6 7.2 10.8 3.6 — — dose, µg/kg

Day of ANC recovery 16 15 16 16 16 15 15 14 15.5 15 15 NS to 0.5 × 109/L, (15-16) (15-16) (14-17) (14-18) (15-16) (14-17) (15-17) (8-15) (14-17) (8-18) (13-16) median (range) Day of platelet 15 18 14 15 22 16 16 15 15.5 16 15 NS recovery to 20 ×109/L, (12-16) (15-18) (14-18) (13-18) (18-27) (15-25) (14-19) (7-15) (13-17) (7-27) (12-21) median (range) No. of platelet 3.0 4.0 2.0 3.0 7.0 3.0 3.0 1.0 2.0 3.0 ND ND transfusion events, (1-5) (3-7) (2-4) (2-4) (3-17) (1-16) (2-8) (1-2) (1-3) (1-17) median (range)

*P values are for comparison of rhTPO-treated groups overall (n = 32) with controls (n = 35). See Table 1 footnotes for descriptions of patient groups.

554 rhTPO for PBPC Mobilization more leukaphereses, only 2 of every 3 patients reach target therapy and G-CSF. The enhanced mobilization by rhTPO hematopoietic progenitor cell counts, and some patients fail combined with chemotherapy and G-CSF could provide to achieve the minimum dose necessary for transplantation. several benefits. Reduction in the number of required leuka- The combination of high-dose chemotherapy and G-CSF is phereses could reduce patient discomfort and inconvenience often used to enhance yields beyond those that can be while saving money, resources, and staff time, which achieved with G-CSF alone while providing further cancer increase along with the number of PBPC collection and cytoreduction [9]. storage procedures. Studies have suggested that decreasing In this study, we evaluated the safety of rhTPO adminis- the number of PBPC collections minimizes the risk of tered according to several doses and schedules and its ability tumor cell contamination in the PBPC products [25-28]. to enhance chemotherapy- and G-CSF-mediated mobiliza- Another benefit is the prospect of greater yields per leuka- tion of PBPCs in patients with advanced breast cancer. The pheresis, which might allow patients to receive multiple results showed that administration of rhTPO in this trial infusions of PBPCs following repeated courses of high-dose was not associated with overt toxicity. Low-grade adverse chemotherapy. Finally, rhTPO may provide a special benefit events considered possibly related to rhTPO might just as by enhancing PBPC numbers in heavily pretreated patients likely have been related to chemotherapy or other drugs. who might otherwise not achieve target yields. Further Excessive thrombocytosis was not a concern. The only studies are warranted, particularly to assess the rhTPO thrombotic events occurred at the sites of central venous effect in patients who mobilize poorly with currently avail- catheters. A specific contribution of rhTPO to these events able mobilization regimens. could not be excluded but clinically seemed unlikely given the timing of the events. There was no evidence of neutralizing anti-TPO antibody formation. Other studies have ACKNOWLEDGMENTS indicated that such antibody formation is a concern, how- Management and support for this study were funded by ever, and future studies must continue to evaluate this risk. Pharmacia Corporation, Peapack, New Jersey, and Genen- rhTPO reduced leukapheresis requirements while tech, Inc, South San Francisco, California. enhancing PBPC cell yields. Significantly more rhTPO- treated patients achieved a target cell count with only 1 leukapheresis than did control-group patients not receiving REFERENCES rhTPO. A trend toward higher numbers of PBPCs was 1. Antman K, Ayash L, Elias A, et al. A phase II study of high-dose observed when patients given rhTPO were compared with cyclophosphamide, thiotepa, and carboplatin with autologous control patients. The small number of patients evaluated at marrow support in women with measurable advanced breast can- each of the dose levels and the variability in PBPC yields cer responding to standard-dose therapy. J Clin Oncol. 1992;10: precluded definitive observation of a dose-response effect. 102-110. However, rhTPO doses ≥1.2 µg/kg given as multiple infu- 2. Ghalie R, Richman CM, Adler SS, et al. Treatment of metastatic sions seemed to provide more effective PBPC mobilization. breast cancer with a split-course high-dose chemotherapy regi- Administration of rhTPO following mobilization chemo- men and autologous bone marrow transplantation. J Clin Oncol. therapy with CVP was also associated with a significantly 1994;12:342-346. faster recovery of platelet count to ≥100 × 109/L. 3. Wallerstein R, Jr., Spitzer G, Dunphy F, et al. A phase II study of Transplantation of rhTPO-mobilized PBPCs was effec- mitoxantrone, etoposide, and thiotepa with autologous marrow tive in supporting patients following high-dose chemo- support for patients with relapsed breast cancer. J Clin Oncol. therapy with CBT. Median time to recovery was ≤16 days 1990;8:1782-1788. for both neutrophils (ANC ≥0.5 × 109/L) and platelets 4. Crown J, Kritz A, Vahdat L, et al. Rapid administration of multi- (platelet count ≥20 × 109/L). However, these median times ple cycles of high-dose myelosuppressive chemotherapy in patients were not different from the 15-day median recovery times with metastatic breast cancer. J Clin Oncol. 1993;11:1144-1149. noted in control patients, and the addition of rhTPO (in 5. Peters WP, Shpall EJ, Jones RB, et al. High-dose combination group C) before and after high-dose CBT chemotherapy alkylating agents with bone marrow support as initial treatment and PBPC transplantation did not further speed posttrans- for metastatic breast cancer. J Clin Oncol. 1988;6:1368-1376. plantation platelet recovery. Although it was hoped that use 6. Somlo G, Doroshow JH, Forman SJ, et al. High-dose chemo- of rhTPO-mobilized PBPCs and application of additional therapy and stem-cell rescue in the treatment of high-risk breast rhTPO to support patients in the transplantation period cancer: prognostic indicators of progression-free and overall sur- would enhance hematologic reconstitution, it is not surpris- vival. J Clin Oncol. 1997;15:2882-2893. ing that these effects were not observed in the current trial. 7. Sheridan WP, Begley CG, Juttner CA, et al. Effect of peripheral- Both treated and control patients were generally early in the blood progenitor cells mobilised by filgrastim (G-CSF) on course of their breast cancer, had undergone relatively little platelet recovery after high-dose chemotherapy. Lancet. 1992;339: prior therapy, and had grafts that were adequate to ensure 640-644. rapid recovery of both neutrophils and platelets. 8. Bensinger W, Singer J, Appelbaum F, et al. 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