Dose Escalation Phase 9.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose levels 13.0 and 17.5 mcg/kg. dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 13.0 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Dose Escalation Phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.

Expansion phase 17.5 mcg/kg.dose Ph I: Mithramycin will be administered in escalating doses to children and adolescents intravenously IV) over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression. If maximum tolerated dose (MTD) in this Ph differs from the recommended adult dose for Ph II, the protocol will be amended. Using a Simon two stage design, mithramycin will be administered IV at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults with Ewing sarcoma with Ewings sarcoma - friend leukemia integration 1 transcription factor (EWS-FLI1) fusion transcript Both Phases will enroll patients simultaneously. Ph II: mithramycin will be administered intravenously at 17.5 microgram/kg over 6 hours once daily for 7 days to be repeated every 28 days until unacceptable toxicity or disease progression to children and adults.