Palbociclib

447.54

447.53

1592732-453-0

G9ZF61LE7G

C49176

L01XE33|L - Antineoplastic and immunomodulating agents

103

1.8

1.3±0.1 g/cm3

200 °C

711.5°C at 760 mmHg

384.1±35.7 °C

1.648

10 mg/ml (isethionate form)

7.4(the secondary piperazine nitrogen) and 3.9 (the pyridine nitrogen)

7.4 (the secondary piperazine nitrogen) and 3.9 (the pyridine nitrogen)

P201, P202, P260, P281, P308+P313, P314, P405, P501

H341

|Danger|H301 (12.5%): Toxic if swallowed [Danger Acute toxicity, oral]|P201, P202, P260, P264, P270, P273, P281, P301+P310, P301+P312, P308+P313, P314, P321, P330, P391, P405, and P501|Aggregated GHS information provided by 8 companies from 6 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

The reported oral Ld50 is of 100 mg/kg.[MSDS] In cases of overdosage, only supportive measures are considered. Palbociclib was showed to present clastogenic activities in _in vitro_ and _in vivo_ assays. As well, it has been reported to produce fetal harm due to its mechanism of action. Lastly, it was shown to increase the incidence of microglial cell tumors in the central nervous system at high doses.

In the large clinical trials, adverse events were common and led to dose reductions in one-third of patients and discontinuation in 8%. Publications on the efficacy and safety of palbociclib rarely mentioned serum ALT elevations or hepatotoxicity. In a study of women with refractory, metastatic breast cancer, serum ALT elevations occurred in 6% [2% over 5 times ULN] receiving palbociclib and fulvestrant compared to 3% [none over 5 times ULN] on fulvestrant alone. Since its approval and more widescale use, there have been several reports of prominent ALT elevations arising after 2 or 3 cycles of palbociclib, that improved on discontinuation and recurred rapidly when restarted. Serum bilirubin and alkaline phosphatase levels were normal and symptoms were not mentioned. In addition, there have been rare reports of patients with refractory metastatic breast cancer who developed pseudocirrhosis within 2 to 3 months of starting palbociclib presenting with fatigue, jaundice and ascites with only modest elevations in serum aminotransferase and alkaline phosphatase levels. Imaging revealed a severely nodular liver, but liver histology showed desmoplastic changes in areas of necrotic metastatic tumor without cirrhosis. The liver also had vascular changes suggestive of sinusoidal obstruction syndrome, changes possibly caused by the dramatic involution of the metastatic tumor tissue combined with vascular damage. Pseudocirrhosis has been reported with other highly successful antineoplastic therapies of cancer metastatic to the liver, but the frequency is rare.

Binding of palbociclib to human plasma proteins in vitro accounts for approximately 85% of the administered dose.

Palbociclib is indicated in combination with [letrozole] as initial endocrine-based therapy for the treatment of human epidermal growth factor receptor type 2 (HER2)-negative and hormone receptor(HR)-positive tumors in adult patients with advanced/metastatic breast cancer. It is as well approved in combination with [fulvestrant] in patients with disease progression with prior endocrine therapy. In the official labeling, the use of palbociclib should be accompanied with either an aromatase inhibition, no restricted to letrozole, as initial endocrine-based therapy in postmenopausal women or in man. The breast cancer starts as a group of cancer cells that grow into and destroy the nearby breast tissue. This growth can spread into other parts of the body which is called metastasis. According to the location of the cancer cells, it can be categorized in ductal carcinoma and lobular carcinoma. However, other types of breast cancer include inflammatory breast cancer, Paget disease of the breast, triple negative breast cancer non-Hodgkin lymphoma and soft tissue sarcoma. In males, breast cancer is usually treated as the cases of postmenopausal women and almost all the cases are ductal carcinoma.|FDA Label|Ibrance is indicated for the treatment of hormone receptor (HR) positive, human epidermal growth factor receptor 2 (HER2) negative locally advanced or metastatic breast cancer:in combination with an aromatase inhibitor;in combination with fulvestrant in women who have received prior endocrine therapy.In pre- or perimenopausal women, the endocrine therapy should be combined with a luteinizing hormone releasing hormone (LHRH) agonist.|Treatment of Ewing sarcoma|Treatment of breast malignant neoplasms|Drug: Palbociclib

Palbociclib is a unique cyclin-dependent kinase inhibitor that is used in combination with aromatase inhibitors in the treatment of postmenopausal women with metastatic breast cancer. Palbociclib is associated with transient and usually mild elevations in serum aminotransferase during therapy and to an unusual form of liver injury called pseudocirrhosis caused by shrinkage of tumor metastases in the liver combined with desmoplastic changes and vascular damage, that can be severe, progressive and even fatal.

Antineoplastic Agents

Due to its mechanism of action, palbociclib inhibits cell growth and suppresses DNA replication in retinoblastoma tumor suppressor gene (RB) proficient cancer cells. As expected, these RB cells present a significant increase in the proportion of cells in G1 state and the presence of palbociclib produces effective dephosphorylation of RB, reduce proliferation and induce senescence causing cell-cycle arrest. In vitro studies showed the potential for palbociclib to reduce cellular proliferation of estrogen receptor-positive breast cancer cell lines through the inhibition of the cell-cycle progression from G1 to S phase. In this study, it was demonstrated that the sensitivity of the cells significantly increased with the expression of _RB1_ and _CCND1_ and low expression of _CDKN2A_. As well, palbociclib, combined with antiestrogens, enhanced _in vivo_ antitumor activity in estrogen receptor-positive breast cancer mouse models. In clinical trials, palbociclib, in combination with letrozole, was shown to significantly increase the progression-free survival (PFS) in patients with metastatic breast cancer without prior endocrine treatment. In the results, the PFS increased from 4.5 to 9.5 months with an overall response rate (ORR) of 24.6%.

Substances that inhibit or prevent the proliferation of NEOPLASMS. (See all compounds classified as Antineoplastic Agents.)|Agents that inhibit PROTEIN KINASES. (See all compounds classified as Protein Kinase Inhibitors.)

Palbociclib presents a linear pharmacokinetic profile and its peak plasma concentration was observed 6-12 hours after oral administration. The oral bioavailability is reported to be of 46% with a steady-state reached after 8 days and a median accumulation ratio of 2.4. The absorption of palbociclib is significantly reduced under fasting conditions and hence, food intake is recommended when this drug is administered.|The main route of elimination of palbociclib is through feces after hepatic metabolism while renal clearance seems to play a minor role accounting only for 17.5% of the eliminated dose.|The mean apparent distribution of palbociclib is 2583 L which suggests that palbociclib penetrates extensively into peripheral tissues.|The mean apparent oral clearance of palbociclib is of 63.1 L/h.

Palbociclib is mainly hepatically transformed. the metabolism is mainly performed by the activities of the cytochrome P450 isoenzyme 3A and the sulfotransferase 2A1. The metabolism of palbociclib is represented mainly by reactions of oxidation and sulfonation followed by acylation and glucuronidation as minor reactions. After its metabolism, palbociclib forms mainly inactive glucuronide and sulfamic acid conjugates. The major circulating metabolite, accounting for 1.5% of the dose in excreta is is the glucuronide conjugate.

The mean plasma elimination half-life of palbociclib is 29 hours.

Palbociclib is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor that acts by binding to the ATP pocket with an IC50 in the range of 9-15 nmol/L. It is important to consider that it presents low to absent activity against other kinases. The CDK4/6 kinase is involved, with coregulatory partner cyclin D, in the G1-S transition. Hence, inhibition of this step prevents cell cycle progression in cells in whose this pathway is functioning. This step includes the pathways of the phosphorylation of retinoblastoma protein and the E2F family of transcription factors.

6-acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-ylpyridin-2-ylamino)-8H-pyrido(2,3-d)pyrimidin-7-one

Human drugs -> Ibrance -> EMA Drug Category|Antineoplastic agents -> Human pharmacotherapeutic group|Human Drugs -> EU pediatric investigation plans|Human Drugs -> FDA Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book) -> Active Ingredients