Backfilling cohorts in phase I dose-escalation studies

BACKGROUND

The use of 'backfilling', assigning additional patients to doses deemed safe, in phase I dose-escalation studies has been used in practice to collect additional information on the safety profile, pharmacokinetics and activity of a drug. These additional patients help ensure that the maximum tolerated dose is reliably estimated and give additional information to determine the recommended phase II dose.

METHODS

In this article, we study the effect of employing backfilling in a phase I trial on the estimation of the maximum tolerated dose and the duration of the study. We consider the situation where only one cycle of follow-up is used for escalation as well as the case where there may be delayed onset toxicities.

RESULTS

We find that, over a range of scenarios, the use of backfilling gives an increase in the percentage of correct selections by up to 9%. On average, for a treatment with a cycle length of 6 weeks, each additional backfilling patient reduces the trial duration by half a week.

CONCLUSIONS

Backfilling in phase I dose-escalation studies can substantially increase the accuracy of estimation of the maximum tolerated dose, with a larger impact in the setting with a dose-limiting toxicity event assessment period of only one cycle. This increased accuracy and reduction in the trial duration are at the cost of increased sample size.

Dose finding studies for therapies with late-onset toxicities: A comparison study of designs

An objective of phase I dose-finding trials is to find the maximum tolerated dose; the dose with a particular risk of toxicity. Frequently, this risk is assessed across the first cycle of therapy. However, in oncology, a course of treatment frequently consists of multiple cycles of therapy. In many cases, the overall risk of toxicity for a given treatment is not fully encapsulated by observations from the first cycle, and hence it is advantageous to include toxicity outcomes from later cycles in phase I trials. Extending the follow up period in a trial naturally extends the total length of the trial which is undesirable. We present a comparison of eight methods that incorporate late onset toxicities while not extensively extending the trial length. We conduct simulation studies over a number of scenarios and in two settings; the first setting with minimal stopping rules and the second setting with a full set of standard stopping rules expected in such a dose finding study. We find that the model-based approaches in general outperform the model-assisted approaches, with an interval censored approach and a modified version of the time-to-event continual reassessment method giving the most promising overall performance in terms of correct selections and trial length. Further recommendations are made for the implementation of such methods.

First-in-human dose escalation study of cyclin-dependent kinase-9 inhibitor VIP152 in patients with advanced malignancies shows early signs of clinical efficacy

PURPOSE

To report on the first-in-human phase I study of VIP152 (NCT02635672), a potent and highly selective CDK9 inhibitor.

PATIENTS AND METHODS

Adults with solid tumors or aggressive non-Hodgkin lymphoma (NHL) who were refractory to or had exhausted all available therapies received VIP152 monotherapy as a 30-minute intravenous, once weekly infusion, as escalating doses (5, 10, 15, 22.5, or 30 mg in 21-day cycles) until the maximum tolerated dose (MTD) was determined.

RESULTS

Thirty-seven patients received {greater than or equal to} 1 VIP152 dose, with 30 mg identified as the MTD based on dose-limiting toxicity of grade 3/4 neutropenia. The most common adverse events were nausea and vomiting (75.7% and 56.8%, respectively), all of grade 1/2 severity. Of the most common events, Grade 3/4 events occurring in > 1 patient were neutropenia (22%), anemia (11%), abdominal pain (8%), increased alkaline phosphatase (8%), and hyponatremia (8%). Day 1 exposure for the MTD exceeded the predicted minimum therapeutic exposure and reproducibly achieved maximal pathway modulation; no accumulation occurred after multiple doses. Seven of 30 patients with solid tumors had stable disease (including 9.5 and 16.8 months in individual patients with pancreatic cancer and salivary gland cancer, respectively), and 2 of 7 patients with high-grade B-cell lymphoma with MYC and BCL2/BCL6 translocations (HGL) achieved durable complete metabolic remission (ongoing at study discontinuation, after 3.7 and 2.3 years of treatment).

CONCLUSION

VIP152 monotherapy, administered intravenously once weekly, demonstrated a favorable safety profile and evidence of clinical benefit in patients with advanced HGL and solid tumors.

A Phase I Study of an MPS1 Inhibitor (BAY 1217389) in Combination with Paclitaxel Using a Novel Randomized Continual Reassessment Method for Dose Escalation

PURPOSE

Monopolar spindle 1 (MPS1) kinase inhibitor, BAY 1217389 (BAY) synergizes with paclitaxel. This phase I study assessed the combination of BAY with paclitaxel using a novel randomized continuous reassessment method (rCRM) to improve dose determination.

PATIENTS AND METHODS

Patients with solid tumors were randomized to receive oral BAY (twice daily 2-days-on/5-days-off) with weekly paclitaxel (90 mg/m²) or paclitaxel monotherapy in cycle 1. Dose escalation was guided by CRM modeling. Primary objectives were to assess safety, establish the MTD of BAY, and to evaluate the pharmacokinetic profiles for both compounds. Simulations were performed to determine the contribution of the rCRM for dose determination.

RESULTS

In total, 75 patients were enrolled. The main dose-limiting toxicities were hematologic toxicities (55.6%). The MTD of BAY was established at 64 mg twice daily with paclitaxel. Inclusion of a control arm enabled the definitive attribution of grade ≥3 neutropenia to higher BAY exposure [AUC_0-12 (P< 0.001)]. After determining the MTD, we included 19 patients with breast cancer at this dose for dose expansion. Other common toxicities were nausea (45.3%), fatigue (41.3%), and diarrhea (40.0%). Overall confirmed responses were seen in 31.6% of evaluable patients. Simulations showed that rCRM outperforms traditional designs in determining the true MTD.

CONCLUSIONS

The combination of BAY with paclitaxel was associated with considerable toxicity without a therapeutic window. However, the use of the rCRM design enabled us to determine the exposure-toxicity relation for BAY. Therefore, we propose that the rCRM could improve dose determination in phase I trials that combine agents with overlapping toxicities.

Safety and efficacy of VIP152, a CDK9 inhibitor, in patients with double-hit lymphoma (DHL)

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Background: PTEFb/CDK9-mediated transcription of short-lived anti-apoptotic survival proteins and oncogenes like MCL-1 and MYC plays a critical role in a variety of cancers. VIP152 (formerly BAY 1251152), a potent and highly selective CDK9 inhibitor, has been evaluated in a Phase 1 dose-escalation study in patients with advanced cancer. The maximum tolerated dose was 30 mg once weekly administered in consecutive 21-day cycles, based on neutropenia as the dose-limiting toxicity (JCO 2018;36:2507; NCT02635672). DHL is defined as dual rearrangement of the MYC gene and either the BCL2 or BCL6 genes; the resulting overexpression of MYC and BCL2/BCL6 make it particularly difficult to treat. Patients with DHL have a poor prognosis and no standard of care. Considering the impact of CDK9 inhibition on MYC, an exploratory cohort of patients with DHL was added to the study. Methods: Patients with refractory or relapsed DHL were eligible. VIP152 was administered once weekly as a 30-minute IV infusion on Days 1, 8 and 15 of a 21-day cycle. Tumor response was assessed according to the revised Cheson criteria (2007). Results: To date a total of 7 patients have been enrolled and were evaluable at the time of data cutoff (24NOV2020). The patients were mostly men (6/7 pts, 86%) with a median (range) age of 70 (58-84) years. All patients received ≥2 prior therapies, including 2 patients with bone marrow transplant. Three of 7 patients (29%) had ≥3 prior therapies. The median time on treatment was 22 days (range 8-1361 days). The most common adverse events of any grade were: constipation, fatigue, nausea (each 3/7 pts, 43%) and abdominal pain, diarrhea, lymphocyte count decrease, neutrophil count decrease, skin infection, tumor pain, and vomiting (each 2/7 pts, 29%). Most were Grade 1 and Grade 2. The Grade 3 adverse events were fatigue, lymphocyte count decrease, neutrophil count decrease (each 1/7 pts, 14%) and tumor pain (2/7 pts, 29%). One Grade 4 lymphocyte count decrease was reported. Two patients had a serious adverse event (Grade 3 syncope and Grade 3 tumor pain). Two patients had dosing held for an adverse event; however, no patient withdrew from treatment due to any adverse events. One death occurred due to disease progression. Pharmacodynamic biomarker analysis showed significant reduction of MYC, PCNA, and MCL-1 mRNA in all patients across multiple timepoints. Antitumor activity consisted of 2 complete metabolic responses in 7 patients (29%) based on investigator-assessed FDG-PET scans. Due to the COVID pandemic, the patients withdrew consent after 3.7 and 2.3 years, respectively, of treatment. Both patients were in complete metabolic response. Conclusions: VIP152 had a manageable safety profile, on-target pharmacodynamic activity and signs of durable monotherapy antitumor activity in patients with DHL. These encouraging results warrant further evaluation of VIP152 in patients with MYC-driven lymphoma and solid tumors. Clinical trial information: NCT02635672.

Pasotuxizumab, a BiTE® immune therapy for castration-resistant prostate cancer: Phase I, dose-escalation study findings

Aim: We report results of a first-in-human study of pasotuxizumab, a PSMA bispecific T-cell engager (BiTE®) immune therapy mediating T-cell killing of tumor cells in patients with advanced castration-resistant prostate cancer. Patients & methods: We assessed once-daily subcutaneous (SC) pasotuxizumab. All SC patients developed antidrug antibodies; therefore, continuous intravenous (cIV) infusion was assessed. Results: A total of 47 patients received pasotuxizumab (SC: n = 31, 0.5-172 μg/d; cIV: n = 16, 5-80 μg/d). The SC maximum tolerated dose was 172.0 μg/d. A sponsor change stopped the cIV cohort early; maximum tolerated dose was not determined. PSA responders occurred (>50% PSA decline: SC, n = 9; cIV, n = 3), including two long-term responders. Conclusion: Data support pasotuxizumab safety in advanced castration-resistant prostate cancer and represent evidence of BiTE monotherapy efficacy in solid tumors. Clinical trial registration: NCT01723475 (ClinicalTrials.gov).

Phase I study of pasotuxizumab (AMG 212/BAY 2010112), a PSMA-targeting BiTE (Bispecific T-cell Engager) immune therapy for metastatic castration-resistant prostate cancer (mCRPC)

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Background: mCRPC has a poor prognosis and immunotherapies are largely ineffective. PSMA is a promising therapeutic target in mCRPC. Pasotuxizumab is a PSMA x CD3 BiTE immune therapy that mediates killing of tumor cells by T cells. Methods: NCT01723475 was a first-in-human, multicenter, dose-escalation study in patients (pts) with mCRPC refractory to standard therapy. Pts received continuous IV infusion of pasotuxizumab in cohorts of 3–4 pts. Dose-escalation followed a continuous reassessment methodology. The primary objective was to determine safety and maximum tolerated dose (MTD); secondary objectives included pharmacokinetics, biomarkers, and tumor response. Results: 16 pts were enrolled into 5 dosing cohorts (5 µg/d, n=3; 10 µg/d, n=4; 20 µg/d, n=3; 40 µg/d, n=4; 80 µg/d, n=2). All pts had ≥1 AE of any grade; most common were fever (94%), chills (69%), and fatigue (50%). 13 pts (81%) had ≥1 AE of grade ≥3; most common were decreased lymphocytes and infections (both 44%). No grade 5 AE occurred. A serious drug-related AE was reported for 1 pt (fatigue, 20 µg/d). No antidrug antibodies were observed. Recruitment was stopped before MTD was reached to allow initiation of a new study sponsored by Amgen. Antitumor activity as indicated by PSA serum level decline was dose dependent, with a mean best PSA change per dosing cohort vs baseline of +0.74% (5 µg/d), −17.9% (10 µg/d), −37.4% (20 µg/d), −42.5% (40 µg/d) and −54.9% (80 µg/d). PSA decreases ≥50% occurred in 3 pts (n=1 each in 20 µg/d, 40 µg/d, 80 µg/d cohorts). One long-term PSA responder was treated for 14 months (40 µg/d) and one for 19.4 months (80 µg/d). The latter pt showed a complete regression of soft-tissue metastases and marked regression of bone metastases by PSMA-PET/CT, >90% reduction in PSA and alkaline phosphatase, and a significant and durable improvement in disease related symptoms. Conclusions: Pasotuxizumab had an acceptable safety profile and dose-dependent clinical activity in mCRPC pts. There were two long term responders in the dose escalation. This is the first clinical study showing that a BiTE immune therapy can be efficacious in solid tumors. Clinical trial information: NCT01723475.

Abstract CT015: Phase I dose-escalation study of the allosteric AKT inhibitor BAY 1125976 in advanced solid cancer

This open-label, phase I first-in-human study (NCT01915576) of BAY 1125976, a highly specific and potent allosteric inhibitor of AKT1/2, was conducted to evaluate the safety, pharmacokinetics, and maximum tolerated dose (MTD) of BAY 1125976 in patients with advanced solid tumors. A dose expansion in hormone receptor (HR) positive metastatic breast cancer (MBC) patients, enriched for patients harboring the AKT1E17K mutation, was included to evaluate the clinical benefit at the recommended Phase II dose (R2D).79 patients (including 39 MBC patients) were enrolled. Mean age was 56.7 years and 61 (77.2%) patients were female. All patients, except one, had received ≥1 prior line of systemic anticancer therapy. Response was measured using RECIST v.1.1.Oral dose escalation was initiated with a continuous once daily (OD) dosing (21 days/cycle), starting with a liquid formulation for the first two dose steps (10 mg and 20 mg OD) and bridging to a tablet formulation for further dose steps (40 mg, 80mg and 120mg OD). Based on toxicity assessment during cycle 1, and additional pharmacokinetic and pharmacodynamic (p-AKT, p-PRAS40 in platelet rich plasma) data, a separate dose escalation using twice daily (BID) dosing tested 40 mg, 60mg and 80mg BID, respectively. The following dose limiting toxicities (DLT) occurred: At 120 mg OD, grade 3 and 4 liver enzyme elevation in two out of 6 patients (2/6) and grade 3 alkaline phosphatase elevation in one patient; at 80mg BID, grade 3 liver enzyme elevation in two out of 4 patients and grade 3 hyperglycemia in one patient. After dose de-escalation according to the continuous reassessment method based study design at 60 mg BID, two out of 6 patients experienced grade 3 liver enzyme elevation. The MTD of BAY 1125976 was determined as 80 mg OD and 60 mg BID, respectively. 28 patients with HR+ MBC were enrolled in the expansion cohort using BAY 1125976 60 mg BID, including nine patients with the AKT1E17K mutation.Pharmacological inhibition of AKT1/2 as shown by inhibition of p-AKT and p-PRAS40 was seen in platelet rich plasma samples. However, among the 78 patients evaluable for response, only 1 (1%) patient with HR+ MBC (AKT1 wild-type) had a partial response (PR), 30 (38%) patients had stable disease (SD) and 38 (49%) patients had progressive disease as best response (data missing from 9 patients). Among 43 patients treated at the R2D, CBR was 27.9%. AKT1E17K mutation status was not associated with tumor response. Molecular characterization of archived tumor samples revealed additional mutations (e.g. PIK3CA, BRCA1/2, KRAS, MYC or FGFR1/2), which may have influenced therapeutic response.In conclusion: Tolerable doses of BAY 1125976 resulted in inhibition of AKT1/2 signaling in platelet rich plasma samples. A notable CBR of 27.9% was achieved at the R2D of BAY 1125976; however PR was seen in only 1 patient with HR+ MBC. Clinical benefit did not correlate with presence of AKT mutations.

Citation Format: Andreas Schneeweiss, Dagmer Hess, Markus Joerger, Andrea Varga, Stacy Moulder, Cynthia Ma, Ian Krop, Sara Hurvitz, Christine Rentzsch, Marion Rudolph, Oliver Boix, Gary Wilkinson, Lars Lindbom, Eleni Lagkadinou, Matthias Ocker. Phase I dose-escalation study of the allosteric AKT inhibitor BAY 1125976 in advanced solid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT015.

First-in-human trial of the oral ataxia telangiectasia and Rad3-related (ATR) inhibitor BAY 1895344 in patients (pts) with advanced solid tumors

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Background: The ATR kinase is a key regulator of the DNA damage response (DDR) machinery, activated by DNA damage and replication stress. BAY 1895344 is a novel, potent, and selective ATR inhibitor with anti-tumor activity in preclinical models with DDR defects. Methods: Pts with advanced metastatic solid tumors resistant or refractory to standard treatment, with and without DDR defects, received BAY 1895344 BID, 3 days (d) on/4 d off continuously in 3-weekly cycles. Results: As of December 20, 2018, 18 pts with colorectal (4), breast (3), prostate (2), and ovarian (2) cancers were enrolled across 6 cohorts (5 mg, 10 mg, 20 mg, 40 mg, 60 mg, and 80 mg BID). Median prior lines of treatment was 5. No dose-limiting toxicities (DLTs) were reported in the 5-40 mg cohorts. 2/3 pts had DLTs in the 80 mg cohort (grade [G] 4 neutropenia, G4 neutropenia and G4 thrombocytopenia) and 2/7 had DLTs in the 60 mg cohort (G4 neutropenia, G2 fatigue). 40 mg BID 3 on/4 off was defined as the maximum tolerated dose. Most common treatment-emergent adverse events included anemia, neutropenia, nausea, and fatigue. Pharmacokinetics appeared dose proportional. Pharmacodynamic analyses showed modulation of pH2AX and/or pKAP1 in paired tumor biopsies at exposures associated with preclinical anti-tumor activity. In 13 pts with and without DDR defects treated at dose levels ≥40 mg BID, the objective response rate was 30.7%, including 2/2 pts at 40 mg (appendix and urothelial cancer), 1/8 pts at 60 mg (breast), and 1/3 pts at 80 mg (endometrial). All responders had ATM protein loss of expression and/or ATM mutation; median treatment duration was 347 d (range 293-364 d). A BRCA1-mutant, olaparib-resistant ovarian cancer pt (60 mg) had a CA125 response and stable disease >10 months. 41 additional pts have been enrolled in ongoing expansion cohorts in cancers with DDR defects (prostate, breast, gynecologic, colorectal) or ATM protein loss (all comers) with responses observed. Conclusions: The ATR inhibitor BAY 1895344 is tolerated at biologically active doses with anti-tumor activity against cancers with certain DDR defects, including ATM protein loss. Clinical trial information: NCT03188965.

Phase 1 study of pasotuxizumab (BAY 2010112), a PSMA-targeting Bispecific T cell Engager (BiTE) immunotherapy for metastatic castration-resistant prostate cancer (mCRPC)

5034

Background: mCRPC has a poor prognosis and immunotherapies are largely ineffective. PSMA is a promising therapeutic target in mCRPC, and pasotuxizumab is a PSMA x CD3 BiTE that mediates tumor cell killing. Methods: NCT01723475 was a first-in-human, multicenter, dose-escalation study in patients (pts) with mCRPC refractory to standard therapy. Pts received pasotuxizumab as a continuous intravenous infusion in cohorts of 3–4 pts. Dose-escalation followed a continuous reassessment methodology design. The primary objective was to determine safety and maximum tolerated dose (MTD); secondary objectives included pharmacokinetics, biomarkers, and tumor response. Results: 16 pts were enrolled into 5 dosing cohorts (5 µg/d, n = 3; 10 µg/d, n = 4; 20 µg/d, n = 3; 40 µg/d, n = 4; 80 µg/d, n = 2). All pts had ≥1 AE of any grade; most common were fever (94%), chills (69%), and fatigue (50%). 13 pts (81%) had ≥1 AE of grade ≥3; most common were decreased lymphocytes and infections (both 44%). No grade 5 AE occurred. A serious AE related to study drug was reported for 1 pt (fatigue, 20 µg/d). No anti-drug antibodies were observed. Recruitment was stopped before MTD was reached to facilitate initiation of a new study sponsored by Amgen. Antitumor activity as indicated by PSA serum level decline was dose dependent, with a mean best PSA change per dosing cohort versus baseline of +0.74% (5 µg/d), –17.9% (10 µg/d), –37.4% (20 µg/d), –42.5% (40 µg/d) and –54.9% (80 µg/d). PSA decreases of ≥50% occurred in 3 pts (n = 1 each in 20 µg/d, 40 µg/d, and 80 µg/d cohorts). One long-term PSA responder was treated for 14 months (40 µg/d) and one for 19.4 months (80 µg/d). The latter pt showed a complete regression of soft-tissue metastases and marked regression of bone metastases as assessed by PSMA-PET/CT, > 90% reduction in PSA and alkaline phosphatase, and a significant and durable improvement in disease related symptoms. Conclusions: Pasotuxizumab had an acceptable safety profile and dose-dependent clinical activity in mCRPC pts. There were two long term responders in the dose escalation. This is the first clinical study showing that a BiTE immunotherapy can be efficacious in solid tumors. Clinical trial information: NCT01723475.

A phase I open-label trial evaluating the cardiovascular safety of regorafenib in patients with advanced cancer

PURPOSE

To characterize the cardiovascular safety profile of regorafenib in patients with advanced cancer.

METHODS

Patients received regorafenib 160 mg/day for 21 days followed by a 7-day break. The primary endpoint was the change from baseline in QTcF at the regorafenib t(max) (Day 21, Cycle 1 or 2) and changes in left ventricular ejection fraction (LVEF) from baseline on Cycle 2, Day 21. Secondary objectives were pharmacokinetics, safety, anti-tumor activity and effects on electrocardiogram intervals. QT intervals were corrected using the methods of Fridericia (QTcF) and Bazett (QTcB). LVEF was assessed by multigated acquisition scanning.

RESULTS

Fifty-three patients were enrolled, and all received at least one dose of regorafenib 160 mg. Twenty-five patients received regorafenib for 21 days without dose reduction. The mean change from baseline in QTcF at t(max) was (-)2 ms (90 % CI -8, 3). No patient experienced a change from baseline in QTcF > 60 ms, and two had QTcF changes between 30 and 60 ms. No patient had a QTcF or QTcB > 480 ms. In 27 patients who received at least 80 mg of regorafenib, the mean change from baseline in LVEF% ± SD was 1.7 ± 7.8. In 14 patients without a dose reduction, the mean change from baseline in LVEF% was (-)0.1 ± 8.6 at Cycle 2, Day 21. Four patients experienced a LVEF decrease between 10 and 20 %.

CONCLUSION

The effects of regorafenib on the QT/QTc interval and LVEF were modest and unlikely to be of clinical significance in the setting of advanced cancer therapy.

Regorafenib in combination with FOLFOX or FOLFIRI as first- or second-line treatment of colorectal cancer: results of a multicenter, phase Ib study

Background

Metastatic colorectal cancer (mCRC) is commonly treated with 5-fluorouracil, folinic acid, and oxaliplatin or irinotecan. The multitargeted kinase inhibitor, regorafenib, was combined with chemotherapy as first- or second-line treatment of mCRC to assess safety and pharmacokinetics (primary objectives) and tumor response (secondary objective).

Patients and methods

Forty-five patients were treated every 2 weeks with 5-fluorouracil 400 mg/m² bolus then 2400 mg/m² over 46 h, folinic acid 400 mg/m², and either oxaliplatin 85 mg/m² or irinotecan 180 mg/m². On days 4–10, patients received regorafenib 160 mg orally once daily.

Results

The median duration of treatment was 108 (range 2–345 days). Treatment was stopped for adverse events or death (17 patients), disease progression (11 patients), and consent withdrawal or investigator decision (11 patients). Six patients remained on regorafenib at data cutoff (two without chemotherapy). Drug-related adverse events occurred in 44 patients [grade ≥3 in 32 patients: mostly neutropenia (17 patients) and leukopenia, hand–foot skin reaction, and hypophosphatemia (four patients each)]. Thirty-three patients achieved disease control (partial response or stable disease) for a median of 126 (range 42–281 days).

Conclusion

Regorafenib had acceptable tolerability in combination with chemotherapy, with increased exposure of irinotecan and SN-38 but no significant effect on 5-fluorouracil or oxaliplatin pharmacokinetics.

Continuous-dose regorafenib (REG) in hepatocellular carcinoma (HCC): Phase I safety and pharmacokinetic (PK) study

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Background: REG is a novel oral inhibitor of multiple kinases involved in angiogenesis, oncogenesis, and tumor microenvironment. A multicenter, open-label, single-arm phase I dose-escalation study evaluated REG given with a continuous schedule and established 100 mg once daily as the maximum tolerated dose. This study explored the safety and PK of this dose in an expanded cohort of advanced HCC pts. Methods: Adults with advanced treatment-refractory HCC (Child Pugh [CP] A or B) received REG 100 mg daily until tumor progression, unacceptable toxicity, or pt/investigator decision to stop. Safety and PK were primary endpoints. Tumor response was a secondary endpoint. Results: The HCC expansion cohort included 20 pts: male/female ratio: 14/6; 10 Asian, 4 white, 4 Hispanic, 1 black, 1 other; mean age: 56.8 ± 13.5 years; 16 CP A, 4 CP B; 2 stage II, 3 stage IIIA, 1 stage IIIC, 13 stage IV; 14 pts had disease progression at entry; 11 pts had 2+ metastatic sites; 19 pts had received prior sorafenib. Median duration of treatment was 42 days (range 23–329); 2 pts were still on treatment at data cutoff. Two pts died during the study (both due to disease progression). Drug-related AEs were reported in 18 pts (90%). The most common grade 3+ drug-related AEs were hypertension (n=4, 20%), fatigue (n=2, 10%), hand-foot skin reaction (n=2, 10%), pain (n=1, 5%), and hemoglobin, ALT, AST, lipase, and other metabolic/laboratory abnormalities (n=1, 5% each). Nine pts required REG dose modifications, and 2 pts stopped treatment permanently because of drug-related AEs. No drug-related serious AEs were reported. Single-dose PK data (cycle 1, day 1) were available from 18 pts, but only 1 pt was evaluable for steady-state PK samples. Single-dose analysis did not indicate any effect of CP status on REG PK. One pt had a partial response and 6 pts had stable disease; median time to progression was 36 days (range 28-237). Conclusions: Continuous-dose REG 100 mg once daily was well tolerated in pts with advanced HCC that progressed on prior sorafenib. PK data obtained after a single 100 mg dose did not indicate any effect of CP status on the PK of REG or its primary metabolites. Disease control was achieved in 7 pts. Clinical trial information: NCT01117623.

Regorafenib (BAY 73-4506) in advanced colorectal cancer: a phase I study

BACKGROUND

In a phase I dose-escalation study, regorafenib demonstrated tolerability and antitumour activity in solid tumour patients. The study was expanded to focus on patients with metastatic colorectal cancer (CRC).

METHODS

Patients received oral regorafenib 60-220 mg daily (160 mg daily in the extension cohort) in cycles of 21 days on, 7 days off treatment. Assessments included toxicity, response, pharmacokinetics and pharmacodynamics.

RESULTS

Thirty-eight patients with heavily pretreated CRC (median 4 prior lines of therapy, range 0-7) were enrolled in the dose-escalation and extension phases; 26 patients received regorafenib 160 mg daily. Median treatment duration was 53 days (range 7-280 days). The most common treatment-related toxicities included hand-foot skin reaction, fatigue, voice change and rash. Twenty-seven patients were evaluable for response: 1 achieved partial response and 19 had stable disease. Median progression-free survival was 107 days (95% CI, 66-161). At steady state, regorafenib and its active metabolites had similar systemic exposure. Pharmacodynamic assessment indicated decreased tumour perfusion in most patients.

CONCLUSION

Regorafenib showed tolerability and antitumour activity in patients with metastatic CRC. This expanded-cohort phase I study provided the foundation for further clinical trials of regorafenib in this patient population.

A phase I dose-escalation study of regorafenib (BAY 73-4506), an inhibitor of oncogenic, angiogenic, and stromal kinases, in patients with advanced solid tumors

PURPOSE

Regorafenib is a novel oral multikinase inhibitor of angiogenic (VEGFR1-3, TIE2), stromal (PDGFR-β, FGFR), and oncogenic kinases (KIT, RET, and RAF). This first-in-man, phase I dose-escalation study assessed the safety, pharmacokinetic, pharmacodynamic, and efficacy profiles of regorafenib in patients with advanced solid tumors.

PATIENTS AND METHODS

Patients aged 18 years or older with advanced solid tumors refractory to standard treatment were recruited. Regorafenib was administered orally for 21 days on/seven days off in repeating cycles, until discontinuation due to toxicity or tumor progression. Adverse events (AE) were assessed using National Cancer Institute Common Terminology Criteria for Adverse Events v3.0. Pharmacokinetic profiles were measured after a single dose and on day 21. Pharmacodynamic and efficacy evaluations included tumor perfusion assessment using dynamic contrast-enhanced MRI, plasma cytokines, and tumor response using RECIST (v1.0).

RESULTS

Fifty-three patients were enrolled into eight cohorts at dose levels from 10 to 220 mg daily. The recommended dose for future studies was determined to be 160 mg daily, with a treatment schedule of 21 days on/seven days off in repeating 28-day cycles. The most common drug-related grade 3 or 4 AEs were dermatologic AEs (hand-foot skin reaction, rash), hypertension, and diarrhea. Pharmacokinetic analysis revealed a similar exposure at steady state for the parent compound and two pharmacologically active metabolites. Tumor perfusion and plasma cytokine analysis showed biologic activity of regorafenib. Three of 47 evaluable patients achieved a partial response (renal cell carcinoma, colorectal carcinoma, and osteosarcoma).

CONCLUSION

Regorafenib showed an acceptable safety profile and preliminary evidence of antitumor activity in patients with solid tumors.