Pharmacotherapeutic group: antineoplastic agents: plant alkaloids and other natural products, ATC code: L01CE01.
Mechanism of action
The anti-tumour activity of topotecan involves the inhibition of topoisomerase-I, an enzyme intimately involved in DNA replication as it relieves the torsional strain introduced ahead of the moving replication fork. Topotecan inhibits topoisomerase-I by stabilising the covalent complex of enzyme and strand-cleaved DNA which is an intermediate of the catalytic mechanism. The cellular sequela of inhibition of topoisomerase-I by topotecan is the induction of protein-associated DNA single-strand breaks.
Clinical efficacy and safety
Relapsed ovarian cancer
In a comparative study of topotecan and paclitaxel in patients previously treated for ovarian carcinoma with platinum-based chemotherapy (n = 112 and 114, respectively), the response rate (95% CI) was 20.5% (13%, 28%) versus 14% (8%, 20%) and median time to progression 19 weeks versus 15 weeks (hazard ratio 0.7 [0.6, 1.0]), for topotecan and paclitaxel, respectively. Median overall survival was 62 weeks for topotecan versus 53 weeks for paclitaxel (hazard ratio 0.9 [0.6, 1.3]).
The response rate in the whole ovarian carcinoma programme (n = 392, all previously treated with cisplatin or cisplatin and paclitaxel) was 16%. The median time to response in clinical studies was 7.6-11.6 weeks. In patients refractory to or relapsing within 3 months after cisplatin therapy (n = 186), the response rate was 10%.
These data should be evaluated in the context of the overall safety profile of the medicinal product, in particular of the significant haematological toxicity (see section 4.8).
A supplementary retrospective analysis was conducted on data from 523 patients with relapsed ovarian cancer. Overall, 87 complete and partial responses were observed, with 13 of these occurring during cycles 5 and 6 and 3 occurring thereafter. Of the patients who received more than 6 cycles of therapy, 91% completed the study as planned or were treated until disease progression, with only 3% withdrawn for adverse events.
Relapsed SCLC
A phase III study (Study 478) compared oral topotecan plus best supportive care (BSC) (n = 71) with BSC alone (n = 70) in patients who had relapsed following first-line therapy (median time to progression [TTP] from first-line therapy: 84 days for oral topotecan plus BSC, 90 days for BSC alone) and for whom re-treatment with intravenous chemotherapy was not considered appropriate. In the oral topotecan plus BSC group there was a statistically significant improvement in overall survival compared with the BSC alone group (Log-rank p = 0.0104). The unadjusted hazard ratio for the oral topotecan plus BSC group relative to the BSC alone group was 0.64 (95% CI: 0.45, 0.90). Median survival in patients treated with oral topotecan plus BSC was 25.9 weeks (95% C.I. 18.3, 31.6) compared to 13.9 weeks (95% CI: 11.1, 18.6) for patients receiving BSC alone (p = 0.0104).
Patient self-reports of symptoms using an unblinded assessment showed a consistent trend for symptom benefit for oral topotecan plus BSC.
One Phase II study (Study 065) and one Phase III study (Study 396) were conducted to evaluate the efficacy of oral topotecan versus intravenous topotecan in patients who had relapsed ≥90 days after completion of one prior regimen of chemotherapy (see Table 1). Oral and intravenous topotecan were associated with similar symptom palliation in patients with relapsed sensitive SCLC in patient self-reports on an unblinded symptom scale assessment in each of these two studies.
Table 1. Summary of survival, response rate, and time to progression in SCLC patients treated with oral topotecan or intravenous topotecan
| | Study 065 | Study 396 |
| Oral topotecan | Intravenous topotecan | Oral topotecan | Intravenous topotecan |
| (N = 52) | (N = 54) | (N = 153) | (N = 151) |
| Median survival (weeks) (95% CI) | 32.3 (26.3, 40.9) | 25.1 (21.1, 33.0) | 33.0 (29.1, 42.4) | 35.0 (31.0, 37.1) |
| Hazard ratio (95% CI) | 0.88 (0.59, 1.31) | 0.88 (0.7, 1.11) |
| Response rate (%) (95% CI) | 23.1 (11.6, 34.5) | 14.8 (5.3, 24.3) | 18.3 (12.2, 24.4) | 21.9 (15.3, 28.5) |
| Difference in response rate (95% CI) | 8.3 (-6.6, 23.1) | -3.6 (-12.6, 5.5) |
| Median time to progression (weeks) (95% CI) | 14.9 (8.3, 21.3) | 13.1 (11.6, 18.3) | 11.9 (9.7, 14.1) | 14.6 (13.3, 18.9) |
| Hazard ratio (95% CI) | 0.90 (0.60, 1.35) | 1.21 (0.96, 1.53) |
N = total number of patients treated.
CI = Confidence interval.
In another randomised Phase III study which compared intravenous (IV) topotecan to cyclophosphamide, doxorubicin and vincristine (CAV) in patients with relapsed, sensitive SCLC, the overall response rate was 24.3% for topotecan compared to 18.3% for the CAV group. Median time to progression was similar in the two groups (13.3 weeks and 12.3 weeks, respectively). Median survivals for the two groups were 25.0 and 24.7 weeks, respectively. The hazard ratio for survival with IV topotecan relative to CAV was 1.04 (95% CI: 0.78 – 1.40).
The response rate to topotecan in the combined small cell lung cancer programme (n = 480) for patients with relapsed disease sensitive to first-line therapy was 20.2%. Median survival was 30.3 weeks (95% CI: 27.6, 33.4).
In a population of patients with refractory SCLC (those not responding to first-line therapy), the response rate to topotecan was 4.0%.
Cervical carcinoma
In a randomised, comparative Phase III study conducted by the Gynecologic Oncology Group (GOG 0179), topotecan plus cisplatin (n = 147) was compared with cisplatin alone (n = 146) for the treatment of histologically confirmed persistent, recurrent or Stage IVB carcinoma of the cervix where curative treatment with surgery and/or radiation was not considered appropriate. Topotecan plus cisplatin had a statistically significant benefit in overall survival relative to cisplatin monotherapy after adjusting for interim analyses (Log-rank p = 0.033).
Table 2. Study results Study GOG-0179
| ITT population |
| | Cisplatin 50 mg/m2 on day 1, every 2l days | Cisplatin 50 mg/m2 on day 1 + Topotecan 0.75 mg/m2 on days 1-3, every 21 days |
| Survival (months) | (n = 146) | (n = 147) |
| Median (95% CI) | 6.5 (5.8, 8.8) | 9.4 (7.9, 11.9) |
| Hazard ratio (95% CI) | 0.76 (0.59, 0.98) |
| Log rank p-value | 0.033 |
| Patients without prior cisplatin chemoradiotherapy |
| | Cisplatin | Topotecan/Cisplatin |
| Survival (months) | (n = 46) | (n = 44) |
| Median (95% CI) | 8.8 (6.4, 11.5) | 15.7 (11.9, 17.7) |
| Hazard ratio (95% CI) | 0.51 (0.31, 0.82) |
| Patients with prior cisplatin chemoradiotherapy |
| | Cisplatin | Topotecan/Cisplatin |
| Survival (months) | (n = 72) | (n = 69) |
| Median (95% CI) | 5.9 (4.7, 8.8) | 7.9 (5.5, 10.9) |
| Hazard ratio (95% CI) | 0.85 (0.59, 1.21) |
In patients (n = 39) with recurrence within 180 days after chemoradiotherapy with cisplatin, the median survival in the topotecan plus cisplatin arm was 4.6 months (95% CI: 2.6, 6.1) versus 4.5 months (95% CI: 2.9, 9.6) for the cisplatin arm, with a hazard ratio of 1.15 (0.59, 2.23). In those patients (n = 102) with recurrence after 180 days, the median survival in the topotecan plus cisplatin arm was 9.9 months (95% CI: 7, 12.6) versus 6.3 months (95% CI: 4.9, 9.5) for the cisplatin arm, with a hazard ratio of 0.75 (0.49, 1.16).
Paediatric population
Topotecan was also evaluated in the paediatric population; however, only limited data on efficacy and safety are available.
In an open-label study involving children (n = 108, age range: infant to 16 years) with recurrent or progressive solid tumours, topotecan was administered at a starting dose of 2.0 mg/m2 given as a 30-minute infusion for 5 days repeated every 3 weeks for up to one year depending on response to therapy. Tumour types included were Ewing's sarcoma/primitive neuroectodermal tumour, neuroblastoma, osteoblastoma and rhabdomyosarcoma. Anti-tumour activity was demonstrated primarily in patients with neuroblastoma. Toxicities of topotecan in paediatric patients with recurrent and refractory solid tumours were similar to those historically seen in adult patients. In this study, forty-six (43%) patients received G-CSF over 192 (42.1%) courses; sixty-five (60%) received transfusions of packed red blood cells and fifty (46%) of platelets over 139 and 159 courses (30.5% and 34.9%), respectively. Based on the dose-limiting toxicity of myelosuppression, the maximum tolerated dose (MTD) was established at 2.0 mg/m2/day with G-CSF and 1.4 mg/m2/day without G-CSF in a pharmacokinetic study in paediatric patients with refractory solid tumours (see section 5.2).