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This review highlights strategies to integrate dose optimization into premarketing drug development and discusses the underlying statistical principles. Poor dose optimization can have negative consequences for patients, most commonly because of toxicity, including poor quality of life, reduced effectiveness because of inability of patients to stay on current therapy or receive subsequent therapy because of toxicities, and difficulty in developing combination regimens. We reviewed US Food and Drug Administration initial approvals (2019-2021) of small molecules and antibody-drug conjugates for oncologic indications to determine the proportion with a recommended dosage at the maximum tolerated dose or the maximal administered dose, to characterize the use of randomized evaluations of multiple dosages in dose selection, to describe the frequency of dose modifications at the recommended dosage, and to identify case examples that highlight key principles for premarket dose optimization during drug development. Herein, we highlight major principles for dose optimization and review examples of recent US Food and Drug Administration approvals that illustrate how investigation of dose- and exposure-response relationships and use of randomized dose trials can support dose optimization. Although there has been some progress, dose optimization through randomized dose evaluation in oncology trials is not routinely conducted. Dose optimization is essential to ensure that patients receive therapies which maximize efficacy while minimizing toxicity.

On September 21, 2022, the U.S. Food and Drug Administration (FDA) granted accelerated approval to selpercatinib (Retevmo®, Eli Lilly and Company) for the treatment of adult patients with locally advanced or metastatic solid tumors with a rearranged during transfection (RET) gene fusion that have progressed on or following prior systemic treatment or who have no satisfactory alternative treatment options. The approval was based on data from Study LOXO-RET-17001 (LIBRETTO-001; NCT03157128), an international, non-randomized, multi-cohort clinical trial which included patients with advanced solid tumors harboring RET alterations. The overall response rate (ORR) in 41 patients with locally advanced or metastatic RET fusion-positive solid tumors other than non-small cell lung cancer (NSCLC) or thyroid cancer was 44% (95% CI: 28%, 60%) with median duration of response 24.5 months (95% CI: 9.2, not evaluable). Patients with 10 of 14 tumor types with a variety of fusion partners had objective responses, including patients with the following tumors: pancreatic adenocarcinoma, colorectal, salivary, unknown primary, breast, soft tissue sarcoma, bronchial carcinoid, ovarian, small intestine, and cholangiocarcinoma. The recommendation for approval was supported by results from LIBRETTO-001 in patients with RET fusion-positive NSCLC and thyroid cancer, which formed the basis of prior approvals in these tumor types. The most common adverse reactions (>25%) were edema, diarrhea, fatigue, dry mouth, hypertension, abdominal pain, constipation, rash, nausea, and headache. This is the first tissue agnostic approval of a RET-directed targeted therapy.

PURPOSE On March 4, 2022, the US Food and Drug Administration (FDA) approved nivolumab plus platinum-doublet chemotherapy for the neoadjuvant treatment of patients with resectable non–small-cell lung cancer (NSCLC). We discuss the FDA's review of the key data and regulatory considerations supporting this approval. PATIENTS AND METHODS The approval was based on the results of CheckMate 816, an international, multiregional, active-controlled trial that randomly assigned 358 patients with resectable NSCLC, stage IB (≥4 cm) to IIIA (N2) per the American Joint Committee on Cancer seventh staging edition to receive either nivolumab plus platinum-doublet or platinum-doublet chemotherapy alone for three cycles before planned surgical resection. The major efficacy end point that supported this approval was event-free survival (EFS). RESULTS At the first planned interim analysis (IA), the hazard ratio (HR) for EFS was 0.63 (95% CI, 0.45 to 0.87; P = .0052; statistical significance boundary = .0262) favoring the nivolumab plus chemotherapy arm; the median EFS was 31.6 months (95% CI, 30.2 to not reached) in the nivolumab plus chemotherapy arm versus 20.8 months (95% CI, 14.0 to 26.7) in the chemotherapy-only arm. At the time of a prespecified IA for overall survival (OS), 26% of patients had died, and the HR for OS was 0.57 (95% CI, 0.38 to 0.87; P = .0079; statistical significance boundary = .0033). Eighty-three percent of patients in the nivolumab-containing arm versus 75% in the chemotherapy-only arm received definitive surgery. CONCLUSION This approval, the first for any regimen for the neoadjuvant treatment of NSCLC in the United States, was supported by a statistically significant and clinically meaningful improvement in EFS with no evidence of detriment in OS or negative impact on patients' receipt and timing of surgery or surgical outcomes.

On May 8, 2020, the FDA granted accelerated approval to selpercatinib for (i) adult patients with metastatic RET fusion–positive non–small cell lung cancer (NSCLC), (ii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET-mutant medullary thyroid cancer who require systemic therapy, and (iii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET fusion–positive thyroid cancer who require systemic therapy and who are radioactive iodine refractory (if radioactive iodine is appropriate). Approval was granted on the basis of the clinically important effects on the overall response rate (ORR) with prolonged duration of responses observed in a multicenter, open-label, multicohort clinical trial (LIBRETTO-001, NCT03157128) in patients whose tumors had RET alterations. ORRs within the approved patient populations ranged from 64% [95% confidence interval (CI), 54–73] in prior platinum-treated RET fusion–positive NSCLC to 100% (95% CI, 63–100) in systemic therapy–naïve RET fusion–positive thyroid cancer, with the majority of responders across indications demonstrating responses of at least 6 months. The product label includes warnings and precautions for hepatotoxicity, hypertension, QT interval prolongation, hemorrhagic events, hypersensitivity, risk of impaired wound healing, and embryo-fetal toxicity. This is the first approval of a drug specifically for patients with RET alterations globally.

Supplementary Tables 1 - 3

Lung Cancer Staging per AJCC 7th and 8th Editions

On March 10, 2021, the FDA granted regular approval to tivozanib for treatment of patients with relapsed or refractory (R/R) advanced renal cell carcinoma (RCC) following two or more prior systemic therapies. Approval was based on the TIVO-3 study, a randomized trial of tivozanib versus sorafenib in patients with R/R advanced RCC. In TIVO-3, patients were randomized to receive either tivozanib 1.34 mg orally once daily for 21 consecutive days of every 28-day cycle or sorafenib 400 mg orally twice daily continuously. The primary endpoint was progression-free survival (PFS) per RECIST v1.1. Tivozanib demonstrated efficacy compared with sorafenib with an improvement in PFS [HR, 0.73; 95% confidence interval (CI), 0.56–0.95; P = 0.016]. The estimated median PFS was 5.6 months and 3.9 months in the tivozanib and sorafenib arms, respectively. There was no evidence of a detrimental effect on overall survival: HR, 0.97 (95% CI, 0.75–1.24). The most common grade 3 to 4 adverse reaction on the tivozanib arm was hypertension (24%). Compared with sorafenib, tivozanib was associated with lower rates of grade 3 to 4 diarrhea, rash, and palmar-plantar erythrodysesthesia. Patients receiving tivozanib in TIVO-3 had lower rates of dose reduction, interruption, or permanent discontinuation than those receiving sorafenib.

The FDA approved capmatinib and tepotinib on May 6, 2020, and February 3, 2021, respectively. Capmatinib is indicated for patients with metastatic non–small cell lung cancer (mNSCLC) whose tumors have a mutation leading to mesenchymal–epithelial transition (MET) exon 14 skipping as detected by an FDA-approved test. Tepotinib is indicated for mNSCLC harboring MET exon 14 skipping alterations. The approvals were based on trials GEOMETRY mono-1 (capmatinib) and VISION (tepotinib). In GEOMETRY mono-1, overall response rate (ORR) per Blinded Independent Review Committee (BIRC) was 68% [95% confidence interval (CI), 48–84] with median duration of response (DoR) 12.6 months (95% CI, 5.5–25.3) in 28 treatment-naïve patients and 41% (95% CI: 29, 53) with median DoR 9.7 months (95% CI, 5.5–13) in 69 previously treated patients with NSCLC with mutations leading to MET exon 14 skipping. In VISION, ORR per BIRC was 43% (95% CI: 32, 56) with median DoR 10.8 months (95% CI, 6.9–not estimable) in 69 treatment-naïve patients and 43% (95% CI, 33–55) with median DoR 11.1 months (95% CI, 9.5–18.5) in 83 previously-treated patients with NSCLC harboring MET exon 14 alterations. These are the first two therapies to be FDA approved specifically for patients with metastatic NSCLC with MET exon 14 skipping.

On December 18, 2020, the FDA approved osimertinib as adjuvant therapy in patients with non–small cell lung cancer (NSCLC) whose tumors have EGFR exon 19 deletions or exon 21 (L858R) mutations, as detected by an FDA-approved test. The approval was based on the ADAURA study, in which 682 patients with NSCLC were randomized to receive osimertinib (n = 339) or placebo (n = 343). Disease-free survival (DFS) in the overall population (stage IB–IIIA) was improved for patients who received osimertinib, with an HR of 0.20; 95% confidence interval (CI), 0.15–0.27; P < 0.0001. Median DFS was not reached for the osimertinib arm compared with 27.5 months (95% CI, 22.0–35.0) for patients receiving placebo. Overall survival data were not mature at the time of the approval. This application was reviewed under FDA's Project Orbis, in collaboration with Australia Therapeutic Goods Administration, Brazil ANVISA, Health Canada, Singapore Health Sciences Authority, Switzerland Swissmedic, and the United Kingdom Medicines and Healthcare products Regulatory Agency. This is the first targeted therapy adjuvant approval for NSCLC and has practice-changing implications.

On April 17, 2020, the FDA granted accelerated approval to pemigatinib (PEMAZYRE, Incyte Corporation) for the treatment of adults with previously treated, unresectable locally advanced or metastatic cholangiocarcinoma with an FGFR2 fusion or other rearrangement as detected by an FDA-approved test. Approval was based on FIGHT-202 (NCT02924376), a multicenter open-label single-arm trial. Efficacy was based on 107 patients with locally advanced unresectable or metastatic cholangiocarcinoma whose disease had progressed on or after at least one prior therapy and had an FGFR2 gene fusion or rearrangement. Patients received pemigatinib, 13.5 mg orally, once daily for 14 consecutive days, followed by 7 days off therapy. Safety was based on a total of 466 patients, 146 of whom had cholangiocarcinoma and received the recommended dose. Efficacy endpoints were overall response rate (ORR) and duration of response (DOR) determined by an independent review committee using RECIST 1.1. ORR was 36% (95% confidence interval: 27–45). Median DOR was 9.1 months. The most common adverse reactions were hyperphosphatemia, alopecia, diarrhea, nail toxicity, fatigue, dysgeusia, nausea, constipation, stomatitis, dry eye, dry mouth, decreased appetite, vomiting, arthralgia, abdominal pain, hypophosphatemia, back pain, and dry skin. Ocular toxicity and hyperphosphatemia are important risks of pemigatinib. The recommended dosage is 13.5 mg orally once daily for 14 consecutive days followed by 7 days off therapy in 21-day cycles. FDA also approved the FoundationOne CDX (Foundation Medicine, Inc.) as a companion diagnostic for patient selection.

On September 15, 2021, the FDA granted accelerated approval to mobocertinib (Exkivity, Takeda Pharmaceuticals USA, Inc.) for the treatment of adult patients with locally advanced or metastatic non–small cell lung cancer (NSCLC) with EGFR exon 20 insertion mutations, as detected by an FDA-approved test, whose disease has progressed on or after platinum-based chemotherapy. The approval was based on data from Study AP32788–15–101 (NCT02716116), an international, non-randomized, multi-cohort clinical trial that included patients with locally advanced or metastatic NSCLC with EGFR exon 20 insertion mutations. The overall response rate in 114 patients whose disease had progressed on or after platinum-based chemotherapy was 28% [95% confidence interval (CI), 20%–37%] with a median duration of response of 17.5 months (95% CI, 7.4–20.3). The most common adverse reactions (>20%) were diarrhea, rash, nausea, stomatitis, vomiting, decreased appetite, paronychia, fatigue, dry skin, and musculoskeletal pain. Product labeling includes a Boxed Warning for QTc prolongation and torsades de pointes. This is the first approval of an oral targeted therapy for patients with advanced EGFR exon 20 insertion mutation–positive NSCLC.

On May 8, 2020, the FDA granted accelerated approval to selpercatinib for (i) adult patients with metastatic RET fusion–positive non–small cell lung cancer (NSCLC), (ii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET-mutant medullary thyroid cancer who require systemic therapy, and (iii) adult and pediatric patients ≥12 years of age with advanced or metastatic RET fusion–positive thyroid cancer who require systemic therapy and who are radioactive iodine refractory (if radioactive iodine is appropriate). Approval was granted on the basis of the clinically important effects on the overall response rate (ORR) with prolonged duration of responses observed in a multicenter, open-label, multicohort clinical trial (LIBRETTO-001, NCT03157128) in patients whose tumors had RET alterations. ORRs within the approved patient populations ranged from 64% [95% confidence interval (CI), 54–73] in prior platinum-treated RET fusion–positive NSCLC to 100% (95% CI, 63–100) in systemic therapy–naïve RET fusion–positive thyroid cancer, with the majority of responders across indications demonstrating responses of at least 6 months. The product label includes warnings and precautions for hepatotoxicity, hypertension, QT interval prolongation, hemorrhagic events, hypersensitivity, risk of impaired wound healing, and embryo-fetal toxicity. This is the first approval of a drug specifically for patients with RET alterations globally.

FDA's approval of cemiplimab-rwlc on February 22, 2021, follows prior approvals of pembrolizumab and atezolizumab for similar indications as first-line treatment for patients with programmed death ligand-1 (PD-L1)–high advanced non–small cell lung cancer (NSCLC). Approvals of these anti–PD-L1 agents were supported by statistically significant and clinically meaningful improvements in overall survival (OS) in international, multicenter, active-controlled randomized trials. In KEYNOTE-024, the OS HR was 0.60 [95% confidence interval (CI), 0.41–0.89; P = 0.005] favoring pembrolizumab over platinum-doublet chemotherapy. In IMpower110, the OS HR was 0.59 (95% CI, 0.40–0.89; P = 0.0106) favoring atezolizumab over platinum-doublet chemotherapy. In Study 1624, the OS HR was 0.68 (95% CI, 0.53–0.87; P = 0.0022) favoring cemiplimab-rwlc over platinum-doublet chemotherapy. The progression-free survival (PFS) effect sizes for these anti–PD-L1 antibodies were also comparable across their respective registrational trials, and their safety profiles were consistent with the anti–PD-L1 class adverse event profile. The consistent survival benefits and manageable toxicity profiles of these single-agent anti–PD-L1 antibodies have established them as important treatment options in the PD-L1–high NSCLC treatment landscape. FDA approvals of these anti–PD-L1 antibodies, based on their favorable benefit-risk profiles, present effective chemotherapy-free therapeutic options for patients with advanced PD-L1–high NSCLC in the United States.

On May 8, 2020, the FDA granted accelerated approval to selpercatinib for (i) adult patients with metastatic

Regorafenib is the first drug approved by the FDA for the treatment of hepatocellular carcinoma that has progressed on sorafenib and is expected to become a standard of care for these patients. This article summarizes the FDA's review of the data submitted in the supplemental New Drug Application and the basis for approval of regorafenib for this new indication., On April 27, 2017, the U.S. Food and Drug Administration approved regorafenib for the treatment of patients with advanced hepatocellular carcinoma (HCC) who had previously been treated with sorafenib. Approval was based on the results of a single, randomized, placebo‐controlled trial (RESORCE) that demonstrated an improvement in overall survival (OS). Patients were randomly allocated to receive regorafenib160 mg orally once daily or matching placebo for the first 21 days of each 28‐day cycle. The trial demonstrated a significant improvement in OS (hazard ratio [HR] = 0.63; 95% confidence interval [CI], 0.50–0.79, p

On December 18, 2015, the FDA granted regular approval to pembrolizumab (KEYTRUDA; Merck Sharp & Dohme Corp.) for treatment of patients with unresectable or metastatic melanoma based on results of two randomized, open-label, active-controlled clinical trials. In trial PN006, 834 patients with ipilimumab-naïve metastatic melanoma were randomized (1:1:1) to pembrolizumab 10 mg/kg i.v. every 2 or 3 weeks until disease progression or ipilimumab 3 mg/kg every 3 weeks for up to four doses. In trial PN002, 540 patients with ipilimumab-refractory metastatic melanoma were randomized (1:1:1) to pembrolizumab 2 or 10 mg/kg i.v. every 3 weeks or to investigator's choice of chemotherapy. In trial PN006, patients randomized to pembrolizumab demonstrated a statistically significant improvement in overall survival compared with ipilimumab [every-2-week arm: hazard ratio (HR) = 0.63; 95% confidence interval (CI), 0.47–0.83; P < 0.001; every-3-week arm: HR = 0.69; 95% CI, 0.52–0.90; P = 0.004]. In both trials, patients receiving pembrolizumab demonstrated statistically significant improvements in progression-free survival. The most common (≥2%) immune-mediated adverse reactions in a pooled safety analysis were hypothyroidism, pneumonitis, and hyperthyroidism. Key considerations for approval were determination of pembrolizumab dose and interpretation of tumor response–based endpoints using RECIST or immune-related RECIST. Clin Cancer Res; 23(19); 5661–5. ©2017 AACR.

On February 19, 2016, the FDA approved palbociclib (Ibrance, Pfizer) for use in combination with fulvestrant (Faslodex, AstraZeneca) for the treatment of women with hormone receptor (HR)-positive, HER2-negative advanced or metastatic breast cancer (MBC) with disease progression following endocrine therapy. The approval was based on the results of a randomized, double-blind, placebo-controlled trial conducted in 521 pre- and postmenopausal women with HR-positive, HER2-negative advanced or MBC. Patients were randomized (2:1) to receive palbociclib plus fulvestrant (n = 347) or placebo plus fulvestrant (n = 174). The primary endpoint was investigator-assessed progression-free survival (PFS). A statistically significant and clinically meaningful improvement in PFS (9.5 months vs. 4.6 months) was observed in patients receiving palbociclib plus fulvestrant [HR 0.46; 95% confidence interval (CI), 0.36–0.59; P < 0.0001]. Safety data confirmed the known adverse reaction profile of palbociclib. The most common adverse reactions (>20%) in patients treated with palbociclib were neutropenia, leukopenia, infections, fatigue, nausea, anemia, stomatitis, headache, diarrhea, and thrombocytopenia. This approval was granted in the context of a prior accelerated approval for palbociclib in combination with letrozole in patients with HR-positive, HER2-negative advanced breast cancer as initial endocrine-based therapy. Clin Cancer Res; 22(20); 4968–72. ©2016 AACR.

On December 10, 2012, the U.S. Food and Drug Administration granted full approval for a modified indication for abiraterone acetate (Zytiga tablets; Janssen Biotech, Inc.) in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC). The approval was based on clinical trial COU-AA-302, which randomly allocated asymptomatic or mildly symptomatic patients with chemotherapy-naïve mCRPC and no visceral metastases to either abiraterone acetate plus prednisone (N = 546) or placebo plus prednisone (N = 542). The coprimary endpoints were radiographic progression-free survival (rPFS) and overall survival (OS). The median rPFS was 8.3 months in the placebo arm and had not yet been reached in the abiraterone acetate arm {HR, 0.43 [95% confidence interval (CI) 0.35–0.52]; P < 0.0001}. A prespecified interim analysis demonstrated an improvement in OS favoring the abiraterone acetate arm [HR, 0.79 (95% CI, 0.66–0.96)] but did not cross the O'Brien-Fleming boundary for statistical significance. Safety data confirmed the known adverse reaction profile of abiraterone acetate. Full approval was granted on the basis of a large magnitude of effect on rPFS, a favorable trend in OS, and internal consistency across multiple secondary endpoints and exploratory patient-reported pain data. This is the first drug approval for mCRPC to use rPFS as the primary endpoint. Importantly, this approval was granted in the context of a prior statistically significant OS benefit that formed the basis of the original April 28, 2011, approval of abiraterone acetate for patients with mCRPC who had received prior chemotherapy containing docetaxel. Clin Cancer Res; 19(24); 6650–6. ©2013 AACR.

A simulation study was done to determine if 72 h is the most informative sampling duration for bioequivalence (BE) determination in paralleldesigned BE studies with drugs that have half-lives of at least 30 h. The impact of absorption and elimination half-lives on informative sampling was evaluated. Two-treatment parallel-designed BE studies using a one-compartment oral absorption model with half-lives of 30 and 350 h was simulated. Area under the curve (AUC) values were truncated at 12–360 h. Experimental BE data [median time to reach the maximum concentration ( T max ) = 20 h and low clearance = 0.192 L/h) indicated a decrease and then an increase in the intrasubject variability [root mean square error (RMSE)] for truncated AUC as a function of time. Simulations supported these findings with the highest probability of passing the BE confidence interval criteria being between 60 and 96 h, depending on half-life and percent coefficient of variation. The 30-h simulation exhibited a minimum in RMSE at 24-h truncation that continued to increase up to 360 h, whereas the 350-h simulation exhibited a minimum at 60 h, which increased after 96 h. Power curves at the 350-h half-life showed higher probabilities of rejection of BE for true test/reference ratios greater than 0.9. For parallel-designed BE studies, sampling beyond 120 h will not affect the BE decision and therefore is unnecessary. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:4337–4346, 2012

On February 3, 2015, the FDA granted accelerated approval to palbociclib (IBRANCE, Pfizer Inc.), an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), for use in combination with letrozole for the treatment of postmenopausal women with estrogen receptor (ER)–positive, HER2-negative advanced breast cancer as initial endocrine-based therapy for their metastatic disease. The approval is based on a randomized, multicenter, open-label phase I/II trial (PALOMA-1) in 165 patients randomized to palbociclib (125 mg orally daily for 21 consecutive days, followed by 7 days off treatment) plus letrozole (2.5 mg orally daily) or letrozole alone. The phase II portion of the trial was divided into two cohorts: cohort 1 enrolled 66 biomarker-unselected patients and cohort 2 enrolled 99 biomarker-positive patients. The major efficacy outcome measure was investigator-assessed progression-free survival (PFS). A large magnitude of improvement in PFS was observed in patients receiving palbociclib plus letrozole compared with patients receiving letrozole alone (HR, 0.488; 95% confidence interval, 0.319–0.748). Multiple sensitivity analyses were supportive of clinical benefit. The most common adverse reaction in patients receiving palbociclib plus letrozole was neutropenia. This article summarizes the FDA thought process and data supporting accelerated approval based on PALOMA-1 that may be contingent upon verification and description of clinical benefit in the ongoing and fully accrued confirmatory trial PALOMA-2. Clin Cancer Res; 21(21); 4760–6. ©2015 AACR.

On April 22, 2014, the FDA granted full approval to siltuximab (SYLVANT for injection; Janssen Biotech, Inc.), a chimeric human-mouse monoclonal antibody to IL6, for the treatment of patients with multicentric Castleman disease (MCD) who are human immunodeficiency virus (HIV) negative and human herpesvirus-8 (HHV-8) negative. The approval was primarily based on the results of a randomized, double-blind trial in which 79 symptomatic patients with MCD were allocated (2:1) to siltuximab plus best supportive care (BSC) or to placebo plus BSC. The primary efficacy endpoint was the proportion of patients in each arm achieving a durable tumor and symptomatic response that persisted for a minimum of 18 weeks without treatment failure. Tumor response was based on independent review of CT scans using the revised Response Criteria for Malignant Lymphoma, and symptomatic response was defined as complete resolution or stabilization of 34 MCD-related signs and symptoms as reported by the investigator. Thirty-four percent of patients in the siltuximab arm and no patients in the placebo arm met the primary endpoint (P = 0.0012). The most common adverse reactions (>10% compared with placebo) during treatment with siltuximab were pruritus, increased weight, rash, hyperuricemia, and upper respiratory tract infection. Clin Cancer Res; 21(5); 950–4. ©2015 AACR.

On August 17, 2011, the U.S. Food and Drug Administration (FDA) approved vemurafenib tablets (Zelboraf, Hoffmann-LaRoche Inc.) for the treatment of patients with unresectable or metastatic melanoma with the BRAFV600E mutation as detected by an FDA-approved test. The cobas 4800 BRAF V600 Mutation Test (Roche Molecular Systems, Inc.) was approved concurrently. An international, multicenter, randomized, open-label trial in 675 previously untreated patients with BRAFV600E mutation–positive unresectable or metastatic melanoma allocated 337 patients to receive vemurafenib, 960 mg orally twice daily, and 338 patients to receive dacarbazine, 1,000 mg/m2 intravenously every 3 weeks. Overall survival was significantly improved in patients receiving vemurafenib [HR, 0.44; 95% confidence interval (CI), 0.33–0.59; P < 0.0001]. Progression-free survival was also significantly improved in patients receiving vemurafenib (HR, 0.26; 95% CI, 0.20–0.33; P < 0.0001). Overall response rates were 48.4% and 5.5% in the vemurafenib and dacarbazine arms, respectively. The most common adverse reactions (≥30%) in patients treated with vemurafenib were arthralgia, rash, alopecia, fatigue, photosensitivity reaction, and nausea. Cutaneous squamous cell carcinomas or keratoacanthomas were detected in approximately 24% of patients treated with vemurafenib. Other adverse reactions included hypersensitivity, Stevens–Johnson syndrome, toxic epidermal necrolysis, uveitis, QT prolongation, and liver enzyme laboratory abnormalities. Clin Cancer Res; 20(19); 4994–5000. ©2014 AACR.

This article summarizes the regulatory evaluation that led to the full approval of enzalutamide (XTANDI, Medivation Inc.) by the U.S. Food and Drug Administration (FDA) on August 31, 2012, for the treatment of patients with metastatic castration-resistant prostate cancer who have previously received docetaxel. This approval was based on the results of a randomized, placebo-controlled trial which randomly allocated 1,199 patients with mCRPC who had received prior docetaxel to receive either enzalutamide, 160 mg orally once daily (n = 800), or placebo (n = 399). All patients were required to continue androgen deprivation therapy. The primary endpoint was overall survival. At the prespecified interim analysis, a statistically significant improvement in overall survival was demonstrated for the enzalutamide arm compared with the placebo arm [HR = 0.63; 95% confidence interval: 0.53–0.75; P < 0.0001]. The median overall survival durations were 18.4 months and 13.6 months in the enzalutamide and placebo arms, respectively. The most common adverse reactions (≥10%) included asthenia or fatigue, back pain, diarrhea, arthralgia, hot flush, peripheral edema, musculoskeletal pain, headache, and upper respiratory infection. Seizures occurred in 0.9% of patients on enzalutamide compared with no patients on the placebo arm. Overall, the FDA's review and analyses of the submitted data confirmed that enzalutamide had a favorable benefit–risk profile in the study patient population, thus supporting its use for the approved indication. The recommended dose is 160 mg of enzalutamide administered orally once daily. Enzalutamide represents the third product that the FDA has approved in the same disease setting within a period of 2 years. Clin Cancer Res; 19(22); 6067–73. ©2013 AACR.

Historically, regulatory assessment of bioequivalence (BE) has relied upon the comparison of rate and extent of drug absorption between products (1). For drugs intended to be absorbed and systemically delivered to the site(s) of activity, this is generally achieved by measuring drug concentrations in an accessible biological fluid such as blood plasma. Typically, a single-dose, two-treatment, two-period, crossover design study is conducted in a limited number of healthy volunteers under fasting and fed conditions. Two products are deemed bioequivalent if the 90% confidence intervals of the geometric mean test/reference ratios for the pharmacokinetic (PK) parameters maximum plasma concentration, for rate (Cmax); area under the plasma concentration–time curve, for extent (AUC0-t); extrapolated total area under plasma curve to time infinity (AUC∞) fall within the limits of 80–125% (2). For the majority of systemically active drug products reviewed by the Office of Generic Drugs (OGD), the “traditional” metrics, AUC and Cmax, are effective measures of BE. However, in cases where rapid onset of action as well as controlled duration of effect is needed for drug efficacy, a partial AUC metric (pAUC, a portion of the total AUC) may be needed to ensure therapeutic equivalency (3). For example, Ritalin LA® (methylphenidate HCl) is a mixed modified release (MMR) formulation designed to release a bolus of drug for rapid onset of activity and a delayed bolus of drug to sustain activity throughout the day (4). Ritalin LA® capsules contain half the dose as IR beads and half the dose as enteric-coated, DR beads. The Food and Drug Administration (FDA) currently recommends using two pAUC metrics, in addition to AUC∞ and Cmax, to assess BE of generics to Ritalin LA® (see Fig. 1) (5). To better understand the rationale for using pAUC metrics for Ritalin LA®, as well as the selection of the time intervals used for pAUCs, it is important to understand the interplay of the MMR drug release profile with the pharmacodynamic (PD) and PK properties of methylphenidate (MPH) (6). Fig. 1 The first (early) pAUC metric, AUC0-T, compares test and reference systemic exposure responsible for early onset of response, while the second (late) pAUC metric, AUCT-t, compares test and reference systemic exposure responsible for sustaining the response ... MPH is used to treat attention deficit disorder (ADD) and has a short half-life (2 h) and duration of efficacy (2–3 h) (4). According the FDA labeling, MPH MMR formulations (Ritalin LA®, Concerta®, and Metadate CD®) can be taken once a day, providing rapid onset of action in the morning and coverage during the day. MPH’s clinical effects can be assessed using the SKAMP (Swanson, Kotkin, Alger, M-Fynne, and Pelham) ratings (7). Thus, the time course of clinical outcome in ADD patients can be related to MPH pharmacokinetics by a PK/PD model. A PK/PD model was developed by comparing the time course of clinical (SKAMP) response to methylphenidate plasma concentrations following dosing with Concerta® and Metadate CD®. The model showed that clinical superiority is expected at any point in time for the formulation with the highest methylphenidate concentration (8). Therefore, a generic of Ritalin LA could potentially have an AUC and Cmax comparable to the RLD, but not be therapeutically equivalent due to differences in the time concentration profile. As previously stated, two products are deemed bioequivalent if the 90% confidence intervals of the test/reference ratios for Cmax, AUC0-t, and AUC∞ fall within the BE limits of 80–125%. The parameter Tmax (the time of the peak plasma concentration) is also evaluated for similarity by the OGD, but not subject to statistical evaluation. If Tmax differs markedly between the test and reference products, OGD consults the relevant clinical division in the Center for Drug Evaluation and Research to determine whether such differences could result in a lack of therapeutic equivalence. However, the observed Tmax in patients taking Ritalin LA® does not occur in some subjects until the MPH from the DR portion of the formulations is being absorbed. Thus, Tmax will not always provide information about whether a generic of Ritalin LA will provide the same onset of activity as the RLD (1,9). In contrast, the PK parameters of the MPH IR products (e.g. Ritalin®) are characteristics of a single release phase. We used the PK data from the IR MPH formulation to have an unbiased estimate of the Tmax of the IR component of the MMR formulation (10). The Tmax of MPH occurs at 2 h, which is also the time at which the peak PD effect of the early portion of Ritalin LA® is observed (4). We analyzed the PK data from FDA submissions and for IR only MPH products Tmax is about 2 ± 0.5 and 3 ± 0.5 h under fasting and fed conditions, respectively. Generally, approximately 95% of observations fall within two standard deviations of the mean. Therefore, pAUCs calculated to 3 h (pAUC0-3) in a fasting BE study and 4 h (pAUC0-4) for a fed BE study should ensure that 95% of the subjects should achieve their desired therapeutic response. Likewise, applying pAUC3-t and pAUC4-t to fasting and fed BE studies, respectively, should ensure that two products are therapeutically equivalent over the later part of the daily dosing interval. The variability of the early pAUC is higher than that of Cmax and AUC∞ under fasting and fed conditions, but reasonable for use in an equivalence test. In conclusion, the use of two pAUCs metrics along with the AUC∞ and Cmax will ensure that the pharmacokinetic profiles and clinical effects of generics of Ritalin LA® are sufficiently similar to the brand name drug. For Ritalin LA®, the first (early) pAUC metric is designed to ensure that 90–95% of the subjects have achieved the optimal early onset of response, while the second (late) pAUC metric assesses the response due to the DR portion of the formulation.

Methylphenidate modified-release products produce early and late peak concentrations critical for treatment of morning and afternoon symptoms of attention deficit hyperactivity disorder (ADHD). Standard bioequivalence (BE) criteria cannot be applied to these products. The performance of partial area under the drug concentration-time curve (PAUC), Cmax and AUCINF to assess BE were independently evaluated for two products. A two-stage analysis was performed on plasma data for two methylphenidate modified-release products (Product 1 and 2). Simulations using the fitted parameters determined how changes in fast absorption rate constant (K0Fast) and fraction available (F1) affected curve shape and BE determination using Cmax, AUCINF and PAUC. The sensitivity of the mean PAUC(test)/PAUC(reference) ratios to changes in K0Fast(test) are product dependent. Product 1 mean PAUC(test)/PAUC(reference) ratios for PAUC0-4h are more responsive to both decreases and increases in K0Fast(test) than Product 2. Product 2 showed a greater response in the mean PAUC(test)/PAUC(reference) ratio for PAUC0-4h when the K0Fast(test) is decreased and less response as the value is increased. PAUC estimated curve shape is sensitive to changes in absorption and are product specific, and may require a new PAUC metric for each drug. A non-product specific metric to assess curve shape is warranted.

Objective: To determine if 72 hours is the most informative sampling duration for the bioequivalence (BE) determination for drugs with half-lives > 30 h when using a parallel study design. Methods: Two-treatment parallel-designed BE studies were simulated. A one-compartment oral absorption model with half-lives of 30 h and 350 h (clearance = 0.224 or 0.019 L/h), distribution volume = 9.7 L, and inter-subject variability for clearance of 75-250% was simulated. The test/reference ratio for fraction available was investigated at 1.0 and 1.25, while the rate constants for absorption (Ka) were simulated at a test/reference ratio of 1 and 4. AUC values truncated at 12-360 h were calculated. Experimental parallel BE studies drugs were also investigated. Key findings: Experimental BE data indicated a decrease and then an increase in the root mean square error (RMSE) or variability as a function of time. Simulations supported these findings with the highest probability of passing the CI being between times 24 and 120 h depending on Ka, half-life, and inter-subject variability. Based on this work, a reduction in the sampling duration of parallel-designed BE studies is recommended. Experimental BE data indicated a decrease and then an increase in the RMSE. The 30-h half-life simulations exhibited a minimum in RMSE that rose to a plateau at 350 h. There was an increase in the probability of rejecting BE with longer sampling times for the 30-h simulations showing a maximum near 300 h while the 350-h half-life simulations showed no maximum. Conclusion: For parallel-designed BE studies, sampling beyond 120 h will not change the BE decision and therefore is unnecessary.