4.1. Therapeutic indications

TUKYSA is indicated in combination with trastuzumab and capecitabine for the treatment of adult patients with HER2‑positive locally advanced or metastatic breast cancer who have received at least 2 prior anti‑HER2 treatment regimens.

4.2. Posology and method of administration

Treatment with TUKYSA should be initiated and supervised by a physician experienced in the administration of anti–cancer medicinal products.

Posology

The recommended dose is 300 mg tucatinib (two 150 mg tablets) taken twice daily continuously in combination with trastuzumab and capecitabine, at doses described in table 1. Refer to the summary of product characteristics (SmPC) for co-administered trastuzumab and capecitabine for additional information. The treatment components can be administered in any order.

Table 1: Recommended dosing

Treatment

Dose

Treatment days

Timing relative to food intake

Tucatinib

300 mg orally

twice daily

Continuously

With or without a meal

Capecitabine

1000 mg/m2 orally

twice daily

Days 1 to 14 every 21 days

Within 30 minutes after a meal

Trastuzumab

Intravenous dosing

Not applicable

Initial dose

8 mg/kg intravenously

Day 1

Subsequent doses

6 mg/kg intravenously

Every 21 days

OR

Subcutaneous dosing

600 mg subcutaneously

Every 21 days

Treatment with TUKYSA should be continued until disease progression or unacceptable toxicity.

Missed dose

In the case of a missed dose, the patient should take their next dose at the regularly scheduled time.

Dose modification

The recommended tucatinib dose modifications for patients with adverse reactions (see section 4.8) are provided in Tables 2 and 3. Refer to the SmPC for co‑administered trastuzumab and capecitabine for dose modifications for toxicities suspected to be caused by those therapies.

Table 2: Recommended tucatinib dose reductions for adverse reactions

Dose level

Tucatinib dose

Recommended starting dose

300 mg twice daily

First dose reduction

250 mg twice daily

Second dose reduction

200 mg twice daily

Third dose reduction

150 mg twice daily1

1. TUKYSA should be permanently discontinued in patients unable to tolerate 150 mg orally twice daily.

Table 3: Recommended tucatinib dose modifications for adverse reactions

Adverse Reaction

Severity1

Tucatinib dosage modification

Diarrhoea

Grade 1 and 2

No dose modification is required.

Grade 3 without anti-diarrheal treatment

Initiate or intensify appropriate medical therapy. Interrupt tucatinib until recovery to ≤ Grade 1, then resume tucatinib at the same dose level.

Grade 3 with anti-diarrheal treatment

Initiate or intensify appropriate medical therapy. Interrupt tucatinib until recovery to ≤ Grade 1, then resume tucatinib at the next lower dose level.

Grade 4

Permanently discontinue tucatinib.

Increased ALT, AST or total bilirubin2

Grade 1 bilirubin (> ULN to 1.5 x ULN)

No dose modification is required.

Grade 2 bilirubin (> 1.5 to 3 × ULN)

Interrupt tucatinib until recovery to ≤ Grade 1, then resume tucatinib at the same dose level.

Grade 3 ALT or AST (> 5 to 20 × ULN)

OR

Grade 3 bilirubin (> 3 to 10 × ULN)

Interrupt tucatinib until recovery to ≤ Grade 1, then resume tucatinib at the next lower dose level.

Grade 4 ALT or AST (> 20 × ULN)

OR

Grade 4 bilirubin (> 10 × ULN)

Permanently discontinue tucatinib.

ALT or AST > 3 × ULN

AND

Bilirubin > 2 × ULN

Permanently discontinue tucatinib.

Other adverse reactions

Grade 1 and 2

No dose modification is required.

Grade 3

Interrupt tucatinib until recovery to ≤ Grade 1, then resume tucatinib at the next lower dose level.

Grade 4

Permanently discontinue tucatinib.

1. Grades based on National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.03

2. Abbreviations: ULN = upper limit of normal; ALT = alanine aminotransferase; AST = aspartate aminotransferase

Co-administration with CYP2C8 inhibitors

Concomitant use with strong CYP2C8 inhibitors should be avoided. If coadministration with a strong CYP2C8 inhibitor cannot be avoided, the starting tucatinib dose should be reduced to 100 mg orally twice daily. After discontinuation of the strong CYP2C8 inhibitor for 3 elimination half-lives, the tucatinib dose that was taken prior to initiating the inhibitor should be resumed (see section 4.4 and section 4.5). Monitoring for TUKYSA toxicity should be increased when administered with moderate CYP2C8 inhibitors.

Special populations

Elderly

No dose adjustment is required in patients aged ≥ 65 years (see section 5.2). Tucatinib has not been investigated in patients above the age of 80 years.

Renal impairment

No dose adjustment is required in patients with mild, moderate, or severe renal impairment (see section 5.2).

Hepatic impairment

No dose adjustment is required in patients with mild or moderate hepatic impairment (see section 5.2). For patients with severe hepatic impairment (Child-Pugh C), a reduced starting dose of 200 mg orally twice daily is recommended.

Paediatric population

The safety and efficacy of TUKYSA in paediatric patients have not been established. No data are available.

Method of administration

TUKYSA is for oral use. The tablets should be swallowed whole and should not be chewed, crushed, or split prior to swallowing (see section 5.2).

TUKYSA should be taken approximately 12 hours apart, at the same time every day, with or without a meal. TUKYSA may be taken at the same time with capecitabine.

4.3. Contraindications

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.

4.4. Special warnings and precautions for use

Laboratory Tests

Increased ALT, AST, and bilirubinIncreased ALT, AST, and bilirubin have been reported during treatment with tucatinib (see section 4.8). ALT, AST, and total bilirubin should be monitored every three weeks or as clinically indicated. Based on the severity of the adverse reaction, treatment with tucatinib should be interrupted, then dose reduced or permanently discontinued (see section 4.2).

Increased creatinine without impaired renal function

Increase in serum creatinine (30% mean increase) has been observed due to inhibition of renal tubular transport of creatinine without affecting glomerular function (see section 4.8). Alternative markers such as BUN, cystatin C, or calculated GFR, which are not based on creatinine, may be considered to determine whether renal function is impaired.

Diarrhoea

Diarrhoea, including severe events such as dehydration, hypotension, acute kidney injury and death, has been reported during treatment with tucatinib (see section 4.8). If diarrhoea occurs, antidiarrheals should be administered as clinically indicated. For Grade ≥3 diarrhoea, treatment with tucatinib should be interrupted, then dose reduced or permanently discontinued (see section 4.2). Prompt medical management should also be instituted in the event of persistence of concomitant Grade 2 diarrhoea with concomitant Grade ≥2 nausea and/or vomiting. Diagnostic tests should be performed as clinically indicated to exclude infectious causes of Grade 3 or 4 diarrhoea or diarrhoea of any grade with complicating features (dehydration, fever, neutropenia).

Embryo-foetal toxicity

Based on findings from animal studies and its mechanism of action, tucatinib may cause harmful effects to the foetus when administered to a pregnant woman. In animal reproduction studies, administration of tucatinib to pregnant rabbits during organogenesis caused foetal abnormalities in rabbits at maternal exposures similar to the clinical exposures at the recommended dose.

Pregnant women should be advised of the potential risk to a foetus. Women of childbearing potential should be advised to use effective contraception during and up to at least 1 week after the last dose of treatment (see section 4.6). Male patients with female partners of childbearing potential should also be advised to use an effective method of contraception during and up to at least 1 week after the last dose of treatment.

Sensitive CYP3A substrates

Tucatinib is a strong CYP3A inhibitor. Thus, tucatinib has the potential to interact with medicinal products that are metabolised by CYP3A, which may lead to increased plasma concentrations of the other product (see section 4.5). When tucatinib is co‑administered with other medicinal products, the SmPC for the other product should be consulted for the recommendations regarding co-administration with CYP3A inhibitors. Concomitant treatment of tucatinib with CYP3A substrates when minimal concentration changes may lead to serious or life–threatening adverse reactions should be avoided. If concomitant use is unavoidable, the CYP3A substrate dosage should be reduced in accordance with the concomitant medicinal product SmPC.

P‑gp substrates

Concomitant use of tucatinib with a P‑gp substrate increased the plasma concentrations of P‑gp substrate, which may increase the toxicity associated with a P‑gp substrate. Dose reduction of P‑gp substrates (including sensitive intestinal substrate such as dabigatran) should be considered in accordance with the concomitant medicine SmPC and P‑gp substrates should be administered with caution when minimal concentration changes may lead to serious or life‑threatening toxicities.

Strong CYP3A/moderate CYP2C8 inducers

Concomitant use of tucatinib with a strong CYP3A or moderate CYP2C8 inducer decreased tucatinib concentrations, which may reduce tucatinib activity. Concomitant use with a strong CYP3A inducer or moderate CYP2C8 inducer should be avoided.

Strong/moderate CYP2C8 inhibitors

Concomitant use of tucatinib with a strong CYP2C8 inhibitor increased tucatinib concentrations , which may increase the risk of tucatinib toxicity. Concomitant use with strong CYP2C8 inhibitors should be avoided (see section 4.2).

There are no clinical data on the impact of concomitant use of moderate CYP2C8 inhibitors on tucatinib concentrations. Monitoring for tucatinib toxicity should be increased with moderate CYP2C8 inhibitors.

Information about excipients

This medicinal product contains 55.3 mg sodium per 300 mg dose. This is equivalent to 2.75% of the recommended maximum daily dietary intake of sodium for an adult.

This medicinal product contains 60.6 mg potassium per 300 mg dose. This should be taken into consideration for patients who have impaired kidney function or are on a controlled potassium diet (diet with low potassium content).

4.5. Interaction with other medicinal products and other forms of interaction

Tucatinib is primarily metabolised by CYP2C8. Tucatinib is a metabolism-based inactivator of CYP3A and inhibits renal transporters of metformin and creatinine. Tucatinib is a substrate of P–gp.

Effects of other medicinal products on tucatinib

CYP3A/CYP2C8 inducers

A clinical drug interaction study found that co-administration of a single dose of 300 mg tucatinib with rifampicin (a strong CYP3A and moderate CYP2C8 inducer) resulted in a reduction in tucatinib concentrations (0.6-fold Cmax (90% CI: 0.5, 0.8) and 0.5-fold AUC (90% CI: 0.4, 0.6)). Co‑administration of tucatinib with strong CYP3A or moderate CYP2C8 inducers such as rifampicin, phenytoin, St. John's wort, or carbamazepine should be avoided as this may result in decreased activity of tucatinib (see section 4.4).

CYP2C8 inhibitors

A clinical drug interaction study found that co-administration of a single dose of 300 mg tucatinib with gemfibrozil (a strong CYP2C8 inhibitor) resulted in an increase in tucatinib concentrations (1.6-fold Cmax (90% CI: 1.5, 1.8) and 3.0-fold AUC (90% CI: 2.7, 3.5)). Co-administration of tucatinib with strong CYP2C8 inhibitors such as gemfibrozil should be avoided as this may result in increased risk of tucatinib toxicity (see section 4.4).

CYP3A inhibitors

A clinical drug interaction study found that co-administration of a single dose of 300 mg tucatinib with itraconazole (a strong CYP3A inhibitor) resulted in an increase in tucatinib concentrations (1.3-fold Cmax (90% CI: 1.2, 1.4) and 1.3-fold AUC (90% CI: 1.3, 1.4)). No dose adjustment is required.

Proton pump inhibitors

Based on clinical drug interaction studies conducted with tucatinib, no drug interactions were observed when tucatinib is combined with omeprazole (a proton pump inhibitor). No dose adjustment is required.

Effects of tucatinib on other medicinal products

CYP3A substrates

Tucatinib is a strong CYP3A inhibitor. A clinical drug interaction study found that co‑administration of tucatinib with midazolam (a sensitive CYP3A substrate) resulted in an increase in midazolam concentrations (3.0‑fold Cmax (90% CI: 2.6, 3.4) and 5.7-fold AUC (90% CI: 5.0, 6.5)). Co‑administration of tucatinib with sensitive CYP3A substrates such as alfentanil, avanafil, buspirone, darifenacin, darunavir, ebastine, everolimus, ibrutinib, lomitapide, lovastatin, midazolam, naloxegol, saquinavir, simvastatin, sirolimus, tacrolimus, tipranavir, triazolam, and vardenafil may increase their systemic exposures which may increase the toxicity associated with a CYP3A substrate. Concomitant use of tucatinib with CYP3A substrates, when minimal concentration changes may lead to serious or life-threatening toxicities, should be avoided. If concomitant use is unavoidable, the CYP3A substrate dosage should be decreased in accordance with the concomitant medicinal product SmPC.

P‑gp substrates

A clinical drug interaction study found that co-administration of tucatinib with digoxin (a sensitive P‑gp substrate) resulted in an increase in digoxin concentrations (2.4‑fold Cmax (90% CI: 1.9, 2.9) and 1.5-fold AUC (90% CI: 1.3, 1.7)). Concomitant use of tucatinib with a P‑gp substrate may increase the plasma concentrations of the P‑gp substrate, which may increase the toxicity associated with the P‑gp substrate. Dose reduction of P‑gp substrates (including sensitive intestinal substrate such as dabigatran) should be considered in accordance with the concomitant medicine SmPC and P‑gp substrates should be administered with caution when minimal concentration changes may lead to serious or life-threatening toxicities (see section 4.4).

CYP2C8 substrates

A clinical drug interaction study found that co-administration of tucatinib with repaglinide (a CYP2C8 substrate) resulted in an increase in repaglinide concentrations (1.7‑fold Cmax (90% CI: 1.4, 2.1) and 1.7‑fold AUC (90% CI: 1.5, 1.9)). No dose adjustment is required.

MATE1/2K substrates

A clinical drug interaction study found that co-administration of tucatinib with metformin (a MATE1/2-K substrate) resulted in an increase in metformin concentrations (1.1-fold Cmax (90% CI: 1.0, 1.2) and 1.4-fold AUC (90% CI: 1.2, 1.5)). Tucatinib reduced the renal clearance of metformin without any effect on glomerular filtration rate (GFR) as measured by iohexol clearance and serum cystatin C. No dose adjustment is required.

CYP2C9 substrates

Based on clinical drug interaction studies conducted with tucatinib, no drug interactions were observed when tucatinib is combined with tolbutamide (a sensitive CYP2C9 substrate). No dose adjustment is required.

4.6. Fertility, pregnancy and lactation

Women of childbearing potential / Contraception in males and females

Based on findings in animals, tucatinib may cause harmful pharmacological effects when administered to women during pregnancy and/or on the foetus/newborn child. Women of childbearing potential should be advised to avoid becoming pregnant and to use effective contraception during and up to at least 1 week after treatment. Male patients with female partners of childbearing potential should also be advised to use effective contraception during and up to at least 1 week after treatment (see section 4.4).

Please also refer to section 4.6 of the prescribing information for trastuzumab and capecitabine.

Pregnancy

There are no data from the use of tucatinib in pregnant women. Studies in animals have shown reproductive toxicity (see section 5.3). TUKYSA should not be used during pregnancy unless the clinical condition of the woman requires treatment with tucatinib. The pregnancy status of women of childbearing potential should be verified prior to initiating treatment with tucatinib. If the patient becomes pregnant during treatment, the potential hazard to the foetus/newborn child must be explained to the patient.

Breast-feeding

It is unknown whether tucatinib/metabolites are excreted in human milk. A risk to the newborns/infants cannot be excluded. Breast‑feeding should be discontinued during treatment with TUKYSA. Breast-feeding may be resumed 1 week after treatment.

Fertility

No fertility studies in men or women have been conducted. Based on findings from animal studies, tucatinib may impair fertility in females of reproductive potential (see section 5.3).

4.7. Effects on ability to drive and use machines

TUKYSA has no or negligible influence on the ability to drive and use machines. The clinical status of the patient should be considered when assessing the patient's ability to perform tasks that require judgment, motor, or cognitive skills.

4.8. Undesirable effects

Summary of the safety profile

The most commonly reported Grade 3 and 4 adverse reactions (≥5%) during treatment are diarrhoea (13%), ALT increased (6%) and AST increased (5%).

Serious adverse reactions occurred in 29% of patients treated with tucatinib, and include diarrhoea (4%), vomiting (3%), and nausea (2%).

Adverse reactions leading to discontinuation of TUKYSA occurred in 6% of patients; the most common adverse reactions leading to discontinuation were diarrhoea (1%) and ALT increased (1%). Adverse reactions leading to dose reduction of TUKYSA occurred in 23% of patients; the most common adverse reactions leading to dose reduction were diarrhoea (6%), ALT increased (5%), and AST increased (4%).

Tabulated list of adverse reactions

The data summarised in this section reflect exposure to TUKYSA in 431 patients with locally advanced unresectable or metastatic HER2-positive breast cancer who received TUKYSA in combination with trastuzumab and capecitabine across two studies, HER2CLIMB and ONT‑380‑005 (see section 5.1). The median duration of exposure to TUKYSA across these studies was 7.4 months (range, <0.1, 43.6).

The adverse reactions observed during treatment are listed in this section by frequency category. Frequency categories are defined as follows: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000); not known (cannot be estimated from the available data).

Table 4. Adverse reactions

System organ class

Frequency

Adverse reaction

Respiratory, thoracic and mediastinal disorders

Very common

Epistaxis

Gastrointestinal disorders

Very common

Diarrhoea, Nausea, Vomiting, Stomatitis1

Skin and subcutaneous tissue disorders

Very common

Rash2

Musculoskeletal and connective tissue disorders

Very common

Arthralgia

Investigations

Very common

AST increase, ALT increase, Blood bilirubin increased3, weight decrease

1. Stomatitis includes stomatitis, oropharyngeal pain, mouth ulceration, oral pain, lip ulceration, glossodynia, tongue blistering, lip blister, oral dysaesthesia, tongue ulceration, aphthous ulcer

2. Rash includes rash maculo-papular, rash, dermatitis acneiform, erythema, rash macular, rash papular, rash pustular, rash pruritic, rash erythematous, skin exfoliation, urticaria, dermatitis allergic, palmar erythema, plantar erythema and skin toxicity

3. Blood bilirubin increased also includes hyperbilirubinemia

Description of selected adverse reactions

Increased ALT, AST, or bilirubin

In HER2CLIMB, increased ALT, AST or bilirubin occurred in 41% of patients treated with tucatinib in combination with trastuzumab and capecitabine. Grade 3 and above events occurred in 9% of patients. Increased ALT, AST or bilirubin led to dose reduction in 9% of patients and treatment discontinuation in 1.5% of patients. The median time to onset of any grade increased ALT, AST, or bilirubin was 37 days; 84% of events resolved, with a median time to resolution of 22 days. Monitoring and dose modification (including discontinuation) should be considered (see section 4.4).

Diarrhoea

In HER2CLIMB, diarrhoea occurred in 82% of patients treated with tucatinib in combination with trastuzumab and capecitabine. Grade 3 and above diarrhoea events occurred in 13% of patients. Two patients who developed Grade 4 diarrhoea subsequently died, with diarrhoea as a contributor to death. Diarrhoea led to dose reduction in 6% of the patients and treatment discontinuation in 1% of the patients. The median time to onset of any grade diarrhoea was 12 days; 81% of diarrhoea events resolved, with a median time to resolution of 8 days. Prophylactic use of antidiarrheals was not required. Antidiarrheal medicinal products were used in less than half of the treatment cycles where diarrhoea events were reported. The median duration of antidiarrheal use was 3 days per cycle (see section 4.4).

Increased creatinine without impaired renal function

Increase in serum creatinine has been observed in patients treated with tucatinib due to inhibition of renal tubular transport of creatinine without affecting glomerular function. In clinical studies, increases in serum creatinine (30% mean increase) occurred within the first cycle of tucatinib, remained elevated but stable throughout treatment and were reversible upon treatment discontinuation.

Special populations

Elderly

In the HER2CLIMB study, 82 patients who received tucatinib were ≥65 years, of whom 8 patients were ≥75 years. The incidence of serious adverse reactions was 34% in patients ≥ 65 years compared to 28% in patients < 65 years. There were too few patients ≥75 years to assess differences in safety.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product.

Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme; website www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9. Overdose

There is no specific antidote, and the benefit of haemodialysis in the treatment of tucatinib overdose is unknown. In the event of an overdose, treatment with tucatinib should be withheld and general supportive measures should be applied.