# Presentation: 484916

## Presented by

- World Health Organization
- at the
- Anti-Infective Drugs
- Advisory Committee
- Meeting
- July 10, 2002

## Global Causes of Deaths 1997

**Infectious and **
**Parasitic diseases**
**          ****33%**

- Unknown
-      12%

- Respiratory
-        6%

- Circulatory system
-           29%

- Cancers
-    12%

- Maternal
-     1%

- Neonatal
-     7%

## MalariaGlobal Context - 1990

- 40% world population
- in exposed areas

## Slide 4

## Slide 5

## Indication

-    Artesunate Rectal Capsules are indicated for the initial management of acute malaria in patients who cannot take medication by mouth and for whom parenteral treatment is not available.

## Slide 7

## Malaria

- 250,000,000 people
- infected
- 1-2 million deaths
- each year

**Malaria**

## Global malaria

- mortality is rising
- >90% of those dying
- from malaria are
- African children

- This is attributed *directly* to
- antimalarial drug resistance

## E I R

- 0

- 10

- 5

- 50

- 20

- AGE

- 100

- 10

- 1

- Cerebral malaria

- Cerebral malaria

- Severe anaemia

- Acute renal failure

- Severe anaemia

- EIR

## Natural History of Malaria Infection

- years

- Parasites

- 0

- 10

- 60

- 5

- 20

- 1013

- 1012

- 1011

- 1010

- 109

- 108

- 107

- 106

- 105

*** ***EIR 50

## Natural History of Malaria Infection

- years

- Parasites

- 0

- 10

- 60

- 5

- 20

- 1013

- 1012

- 1011

- 1010

- 109

- 108

- 107

- 106

- 105

***Entomological Inoculation Rate 50***

## The essential pathological feature of falciparum malaria is the sequestration of erythrocytes containing mature forms of Plasmodium falciparum in the microvasculature of vital organs

- Pongponratn et al. Am J Trop Med Hyg 1991; 44: 168-75

## Cerebral malaria

- Mortality
- 15-20%
- Sequelae
- 3- 10%

## Antimalarial drugs save lives

- because they kill malaria parasites
- Delay in receiving effective
- treatment is the major cause of
- death from malaria

## Artemisinins

- Rapid killing
- Highly active
- Broad stage specificity

- Reduces gametocyte
-  carriage
- No resistance

## Artemisinins

## Pharmacodynamics

- Weeks

**   ****10****12**
**   ****10****10**
**    ****10****8**
**    ****10****6**
**    ****10****4**
**    ****10****2**
**      ****0**

- TOTAL PARASITES

**10**

**10****2**

** ****10****3**

**10****4**

*Detection limit*

**Effect**

**C**

** ****0                   1                   2                  3                  4**

## Worst case scenario

** ****0**

**   ****10****12**
**   ****10****10**
**    ****10****8**
**    ****10****6**
**    ****10****4**
**    ****10****2**
**      ****0**

- TOTAL PARASITES

- WEEKS

** ****1**

** ****2**

- Single administration
- No host defense

## Removing parasites before they can cytoadhere

- 100

- Parasite count (% baseline)

- Additional rings
- removed by artesunate

- Artesunate

- Quinine

- PC90

- PC50

- 50

- 10

**Time (hours)**

## Plasma concentrations (ng/mL)

- ARTESUNATE (i.v. or i.m.)

- ARTEMETHER (i.m.)

- 0

- 12

- 2000

- 1000

- ARTESUNATE rectal capsules

- 8

- 4

- MPC

- HOURS

## ?

*Detection limit*

- 102

- 104

- 106

- 108

- 1010

- 1012

- 1

- 2

- 3

- 4

- 5

- 6

- Total parasites

- weeks

- Emergence
- from the liver

- cycles

## Pathogenicity

- Time (hours)

- cycle

- 7

- 0

- 48

## Moderate

- severity

***CUMULATIVE*****  PROBABILITY **
**OF A FATAL OUTCOME**

- 3%

- Newton & Krishna 1998

- Time (hours)

## Time (hours)

- Severe

*CUMULATIVE*  PROBABILITY
- OF A FATAL OUTCOME

- Newton & Krishna 1998; Schellenberg 1999

## Time (hours)

- OF A FATAL OUTCOME

- ANTIMALARIAL TREATMENT

## Rationale underlying the clinical trials

- Rectal artesunate is a treatment for patients with falciparum malaria who cannot take oral treatment.
- The trials were designed to assess antimalarial activity in-vivo, in the high risk group of patients with high parasitemias, who have not yet developed vital organ dysfunction.
- The focus was on the immediate clinical and parasitological responses, which reflect interruption in the progression to severe malaria and death.

## Patients

- non *per os* /moderately severe malaria
- risk of death without treatment
- single rectal dose of artesunate
- standard consolidation treatment
- all cases were hospitalised

## Endpoints

- Parasitological
- Fractional reduction of parasitemia
-     (12h, 24h, 48h)
- Parasite clearance time
- Clinical response
- fever clearance time
- return to *per os* status
- clinical deterioration
- death
- Adverse events

## Studies

## Parasitological Responses  Studies 5,6,7,14

- Artesunate

- Quinine

## Parasitological Responses 

- Additional rings
- removed by artesunate

- AS

- QN

## Parasitological outcome 7-28 days   

- Parasite positive = any *P.f.* positive smear at
- 7, 14 or 28 days after starting treatment

- Loss to follow up

- 27%

- 38%

- 8%

- Mefloquine: Studies 3, 5; SP: Studies 4, 6, 7; Chloroquine: Study 3

## Clinical findings in patients with recrudescent infections

- 54 patients
- 34 (63 %) patients had fever
- 20 (37%) with symptoms -  vomiting,                          abdominal pain, nausea, cough, headache
- 1 patient temporarily obtunded
- No severe malaria; no deaths

## Representativeness of study population at baseline

## Summary basis for efficacy

- 310 patients (adults and children)
- Varying backgrounds of drug resistance
- Median parasitaemia reduction at 24 h:  99%
- Returned to *per os* status within 24 h:     96%

## Conclusions

- Highly effective
- Consistently rapid parasitological and clinical responses
- Benefit independent of
- age
- geographical location
- background immunity
- race
- antimalarial drug resistance

## Slide 38

## Safety of rectal artesunate

- Context:    to be judged in terms of proposed indication
-                               10 mg/kg body weight once
- Safe in proposed context

**Notes:**
Committee should judge safety in terms of the proposed indication, the risks as opposed to the benefits in the context in which the drug will be used according to the indication that is proposed; that artesunate ranks as the safest of the of drugs within the class of artemisinins; that any of the class adverse effects might indeed apply to artesunate, and we do not contest that position; and that the dose that will be administered compares highly favourably with those doses that have produced toxic effects in experimental animals.   WHO will argue that:

 the main safety issues that have been raised are on the basis of experimental work, rather than on 
    clinical concerns regarding safety;
 In our argument we give higher priority to clinical evidence of safety than to animal data;
 in terms of PK comparisons we submit that no animal satisfactorily serves as a model for comparison with humans, further justifying our argument that human evidence in support of safety supersedes in relevance what has been reported in animals;
 in the class of drugs, artesunate ranks by virtue of its physicochemical properties and in terms of reported human and animal studies as the safest of the class; and 
 neurotoxicity  ranks as the toxic effect of greatest concern, and this is reflected in the FDA briefing document.

WHO will further point out that other issues of toxicity also merit the attention of the advisory committee. 

## Artemisinin neurotoxicity

- Symptomatic 		            Neuropathological
- 	apathy 		            chromatolysis
- 	unsteadiness		necrosis of specific
- 				brainstem nuclei
- 	collapse
- 	coma
- 	death
**                                    **
**                                      **

**Mouse; rat; rhesus monkey; dog**

- Brewer *et al* 1994; Petras *et al.* 1997

- FDA BD p 6-8; WHO BD p 34-37

**Notes:**
Patchy necrosis in isolated neurons was the worst of the lesions verified.   Vestibular, cochlear, olivary, red and other nuclei; that is, principally in brain stem and cerebellar roof.  Various other sites in the spinal cord.  

 Axonal degeneration referred to but this was strange in a number of significant aspects: no associated sign of impending cell death; no loss of neurons; no reactive microglia; no clumping of chromatin; no inflammatory cell infiltration; no collateral evidence of anterograde or retrograde neuronal cell degenerative changes.

  Chromatolysis: enlargement and hyperchromasia; eosinophilic change; swelling of neuronal soma; pyknotic changes in nuclei of nerve cells. 

  More than one laboratory source; including the artemether data.

  Mouse, rat, monkey and dog – class effect; by extension likely to be seen in humans and corresponding conditions of administration.

NOTE: FDA points out that either repeated exposure, and therefore repeated insults, or cumulative doses of artemisiinins administered, or both, may be responsible.  This position and argument of the FDA is, in our view, correct and we must deal with the issue of neurotoxicity comprehensively and on the basis of this argument.

## Slide 41

## Neurotoxicity in the mouse

**Mice with abnormalities of **
**balance and gait       **

**Reversible     Persistent     Total     Deaths**

**Surviving **
**mice with**
**normal balance**
**and gait**

**Treatment (HED)**

**DHA  114 mg/kg                    0                  0                  0             0                20**

**DHA   228 mg/kg                   0                  0                  0             0                20**

**DHA   342 mg/kg                   0                  0                  0             0                20**

**DHA   455 mg/kg                   0                  0                  0             1                19**

**DHA   569 mg/kg                   1                  0                  1             3                16 **

**DHA   683 mg/kg                   2                  0                  2             6                12**

**AS       683 mg/kg                   2                  0                  2             0                18**

**Control (sterile H****2****O)            0                  0                  0             0                20**

- Nontprasert 2000, 2002

**Notes:**
Nontprasert et al:   Transactions Royal Soc Trop Med Hyg (2002), 96, 99-101
                             Am J Trop Med Hyg (2000), 62, 409-412.

Studies deal with high doses of oil soluble artemisinins – artemether and arteether given IM.  Selective damage to the brain stem, predominantly involved in auditory processing and vestibular reflexes.   Constant oral intake is the highest risk compared with other methods of drug intake.   Oral artemether, artesunate and dihydroartemisinin produced no significant clinical or neuropathological evidence of toxicity in doses below 200 mg/kg/d given for 28 days.

The dose causing neurotoxicity or death in 50% of animals was approximately 300 
    mg/kg/d given orally for 28 days  for oral artemether and artesunate compared to 50
    mg/kg/d of IM artemether.   Doses of IM artemether >100mg/kg/d x 28 days were
    invariably fatal.

## Neurotoxicity in the mouse

**Nontprasert 2000**

## 7-day AS toxicity study in rat

- 16                 oral            controls                      -
- 16                 IV              30mg/kg x 7d        34 mg/kg
- 16                 oral            33mg/kg x 7d        37 mg/kg
- 16                 oral            75mg/kg x 3d        39 mg/kg
- 16                 oral            150mg/kg x 2d      48 mg/kg
- 14                 IV              90mg/kg/d x3d      44 mg/kg

- BDC/002; Dayan1998c; Dayan 1998b

**1**
**2**
**3**
**4**
**5**
**6**

**Total AS (mg)**

**HED ****(total)**

**WHO BD 34-37; FDA BD 6-8**

**Notes:**
1.    The study design was based on the artemether and arteether experience in experimental animals, principally reported by WRAIR.  Supervised and neuropathology of each slide scrutinised by Professor A. Dayan, UK.

2.     Group 4:  1 death    (total HED - 39 mg/kg received)
        Group 5:  2 deaths   (total HED – 48 mg/kg received)
        Group 6:  5 deaths   (total HED – 44 mg/kg received) 

The rats were not tolerating higher doses of AS (body weight loss; death; hypoactivity; loose     faeces; reduced food consumption).

   Histopathology studies:  no neurotoxicity.  Staining was with H and E and toluidine blue.
      Histopathology done on all animals except those that had died unattended in the cage, reviewed by 
      Professor Dayan; Staining with H and E; neuropathologists saw the slides.

FDA problems with this approach:

WHO assumes that the total dose of artesunate would be critical in causing neurological or other toxicity; FDA points out that that may or may not be the case, or only part of the case.   For example, it may be that repeated exposure with toxic or subtoxic levels of the drug, rather than the area under the curve of drug exposure, would be the critical toxic event.  Or both.   We concede that FDA is correct in this assertion. 

FDA argues that the WHO the HED is close to the proposed human dose, suggesting a narrow safety margin.   FDA would like to see a safety factor of 10 at least.   WHO concurs.   (This study is inconsistent with the NOAELs reported from all other mouse data.)

iii.  FDA argues that behavioural or other test methods for associated physiological abnormalities in rodents were not conducted and that they are likely to have provided a better indication of histopathology alone.  While this is undoubtedly correct, we have pointed out that:  (I) there is no general agreement about the optimal or recommended nature of functional tests of neurotoxicity affecting the central nervous system; and (ii) neither have such tests been validated in a way that allows for extrapolation from animals to humans. 

iv.   FDA argues that the fact that the toxicity study depended in the mian on H and E staining (toluidine blue staining was also done), vital histopathological evidence of neuronal necrosis and/or demyelination may have been missed.   WHO does not dispute that special stains would have had the capacity to show more clearly evidence of neurohistopathological change, but nonetheless we argue that the WRAIR and artemether findings were principally based on H and E staining and that a leading histopathologist would have missed evidence of histopathology simply because the staining was confined to two stains.  (Most of the original WRAIR findings were based on H and E staining.)

v.   FDA argues that understanding toxic relationships is easier when a pharmacokinetic comparison can be made between the experimental animal models studied and humans.  WHO concurs.  However, no such correlation has been demonstrated.  In view of the lack of detailed information regarding the pharmacokinetics of AS in any experimental animal species, and especially in the animals and at the doses used in toxicity tests, it is problematic to base dose-response considerations on the PK data.

## Repeat human artemisinin exposure

**    **No clinical or neurophysiological toxicity

- Kissinger *et al* 1999; VanVugt *et al.* 2000

- Vietnam:    242 patients and 108 matched controls
- Artemisinin median cumulative exposure 168mg/kg
- Thailand:   79 patients and 79 matched controls
- Artesunate mean cumulative exposure 39mg/kg

**clinical neurological examination**
**audiometry**
**brainstem evoked potential (Vietnam)**
**auditory evoked response (Thailand)**

- WHO BD pp 35-36

**Notes:**
The Vietnamese study is that of Kissinger et al.  (Am J Trop Med Hyg, 2000, 630, 48-55).   Study was by detailed clinical examination, audiometry, and brain stem auditory evoked potentials.   There was no evidence of a drug effect on the clinical or neurophysiological parameters assessed, and no neurophysiological evidence of brain stem toxicity that could be attributed to artemisinin or artesunate.  The patients had received up to 21 antimalarial treatment courses of artemisinin or artesunate alone.

[Tests:  frontal cortex and association areas  primary auditory cortex  medial geniculate body  inferior colliculus  lateral leminiscus  superior olivary complex   cochlear nucleus  acoustic nerve.]

 None of the patients had received mefloquine or other antimalarials, nor the controls.  All the drugs had been given as 5-day regimens.   Adults had received a total of 600 mg artesunate, children proportionately less, and 3000 mg of artemisinin.   Total drug (cumulative) exposure was calculated from whether or not the cumulative amount was less than or equal to 500mg/kg or >500 mg/kg artemisinin or artesunate dose x5.   Note: there were no subjects tested under the age of 5 years.

 Clinical assessment:  hearing abnormalities; vestibular and cerebellar function; control of voluntary movement; auditory localisation; finger to nose movement; Romberg’s test; gait; repetitive alternating movements; fine motor control.   Assessment was done blind to patients’ drug status.

 It is possible, of course, that the assessment tools are not sufficiently sensitive.  

6.   Van Vlugt did the Thailand studies.  Test subjects had received artemether or artesunate on at least 2 occasions in the previous 3 years.    Controls were closely matched, including for history of malaria.   Neurological testing included Romberg’s test, assessment of gait and balance, fine finger dexterity, hearing acuity testing, eye movement testing, nystagmus and behaviour abnormality.   Does not exclude the possibility that the total dose of artemisinin received might be below that associated with toxicity.  Temporo-spatial sound discrimination which relates more closely to higher thalamic and auditory cortical functions might be the more sensitive measurement tool.  The artesunate exposure would have been 12mg/kg/d x 5d or 12 mg/kg/d for 7 days.

## Neurotoxicity - Human Experience

** ****n=1 971 >5 years (307 Artemether; 1 664 Artesunate) **
** ****dose artesunate 12mg/kg over 3-7 days**
** ****Careful neurological examination:**
**heel-to-toe ataxia**
**fine finger dexterity**
**hearing (256Hz tuning fork)**
**assessment for nystagmus and balance**** **
** ****Evaluation at 0, 2, 7 and 28 days after admission**
** ****No deafness or permanent neurological disability**
** **

- Price *et al.* 1999

**Notes:**
Only performed in children more than 5 years old.
 Of all the patients who had neurological abnrmalities (6) – manifested by heel toe ataxia, unable to stand with feet together, nystagmus or impaired finger dexterity all had also received mefloquine as part of the therapeutic regimen.   
In all but one case the neurological abnormality had settled by day 14; in the remaining case (treated with MAS3) – 3 days of AS, the disturbance persisted until day 42 and then disappeared.
 No patient developed permanent neurological abnormality or deafness.

PF: dose and duration details of exposure to the two drugs.

## Human histopathology: Randomised, double-blind comparison of artemether and quinine in severe falciparum malaria

- Full neurological assessment:  560 adults
- audiometry
- assessment of balance at discharge
- 36 deaths artemether; 47 quinine
- total AM exposure 4 – 44 mg/kg
- 21 fatal cases with autopsy
- 15 quinine
- 6 artemether
- No evidence of drug-induced neurotoxicity

- Dayan *et al* 1998; Hien *et al.* 1996

**Notes:**
Hypotension; disseminated intravascular coagulopathy; ischaemia.

## Study 13 – safety update

- Bangladesh; Ghana; Tanzania: double blinded, randomised controlled study
- 99.3% follow up (3342/3366 patients)
- 16 patients had neurological sequelae on follow up

- WHO safety update 2002

**Notes:**
No assessment is yet available on the reversibility of the findings (Ghana; 13/16 cases); 3/3 of the Tanzanian cases resolved on further follow up assessment.

## Neurological Sequelae

- 16 patients identified with neurological sequelae on scheduled follow-up 7-30 days after treatment
- 4/ 16 with confirmed meningitis
- 6/ 16 unconscious at the time of enrolment
- 4 /16 focal neurological sequelae uncharacteristic of drug effect
- 2 /16 (0.05% of 3366) possibly attributable to AS
- 1 unsteady gait
- 1 generalised weakness

## Artemether-Quinine trials

- AQMG 2001

- 1919 patients with severe malaria included in six trials
- Lower mortality in the artemether group but borderline significance

## Preventing death did not increase

-  neurological sequelae

- AQMG 2001

## Neurotoxicity - conclusions

- Class effect
- Artesunate is the safest of the class
- Wide safety margin for proposed indication

**Notes:**
1.  Re-examination of all the available histopathological material at WRAIR by the distinguished US expert neuropathologists Professors Koestner and Graham, and by Professor Tony Dayan of the UK, did not confirm the initial suggestion  of neuronal necrosis in certain brain stem and associated neuronal nuclei. Other, independent studies in rodents and primates, using various artemisinin analogues, have also not reported brain stem neuronal damage except for early work at Chicago, when that diagnosis was made only after consultation with the WRAIR group.

It has been reported in the publication of studies of high-dose artemether by Skelton-Stroud et al done for Novartis and published in Experimental Toxicology and Pathology, 1999, 51, 507-516 (neuropathic lesions were found only when artemether had been administered parenterally for 30 days).

3.    The methods that were employed, and on which we depend for our argument, were applicable for the demonstration of acute neuronal necrosis and its immediate sequelae, and none was seen.   Professors Koestner and Graham have confirmed this.

4.   At the clinical level, the concern is that severe malaria, and possibly repeated attacks of malaria, themselves are believed to be injurious to the brain. The difficulty is to distinguish between the effects on the brain of malaria and those of the drug, and of course to determine whether administration of artesunate might aggravate the potentially injurious effects on the brain of malaria itself. 

5.  The WHO accepts the FDA position that a prima facie case for neurotoxicity of artesunate has been made and that is must be answered to the best extent possible within both experimental and clinical, constraints.   We accept that it remains necessary to explore the issue further clinically, especially in young children, by ongoing detailed monitoring.    We agree with the FDA position that should the indication or method of administration of artesunate be expanded in the future the issues of potential neurotoxicity will undoubtedly become more important, and would need to be comprehensively addressed.

## Slide 53

## Operational StudiesDesign

- Double-blind, placebo-controlled, randomised, multi-centre community-based clinical trial
- Tanzania, Bangladesh and Ghana
- Single-dose administration of AS
- 100 mg in children and 400 mg in adults
- Inclusion criteria: NPO malaria + consent
- Referral to hospital for further treatment
- Follow-up between 7 and 30 days
- Outcome measures:
- mortality and neurological sequelae

## Operational StudiesEnrolled patients

-  Total number of patients: 3366
- Bangladesh: 1459
- Ghana: 991
-  Tanzania: 916

- Status on 19/03/2002

## Operational StudiesEnrolled patients

-  Proportion of patients unconscious at baseline: 11.6% (392/3366 )
-  Proportion of patients with repeated convulsions: 22.8% (768/3366)
-  74.3% (2240/3015) available malaria smears were found to be positive for malaria parasites
-  99.3% (3342/3366) completed follow-up

- Status on 19/03/2002

## Operational StudiesDeaths

|  | Deaths |
| --- | --- |
| Bangladesh | 27/1459 (1.8%) |
| Ghana | 48/991   (4.8%) |
| Tanzania | 24/916   (2.6%) |
| Total | 99/3366 (2.9%) |

- Status on 19/03/2002

-  46%  - 46/99 of patients who died were unconscious at recruitment
-  37% -  36 patients died before reaching hospital
-  43% -  43 patients died at the hospital
-  20% - 20 patients died at home after leaving the hospital

## Operational StudiesData & Safety Monitoring Committee (DSMC)

- Data reviewed  April 4, 2002
- Analyses of the interim results for mortality and neurological sequelae
- Overall analyses, analyses by population and by age:  no reason for interim findings to be unblinded or for the trial protocol to be modified

## Implementation plan

- Controlled, phased deployment
- 5 countries
- Training for mothers and health workers & Traditional Healers
- Ensuring correct use
- Post registration surveillance

## The Malaria Burden

## Place of Death in Children Under 5 years from Acute Febrile Illness with SeizuresMorogoro Rural District - Tanzania

***Based on: "The Policy Implications of Adult Morbidity & Mortality: End of Phase 1 Report" (1997) Tanzania Ministry of Health & AMMP Team, Dar es Salaam.***

## Contact with Formal Health Facilities in the Illness Leading to Death Morogoro Rural District - Tanzania

***Based on: "The Policy Implications of Adult Morbidity & Mortality: End of Phase 1 Report" (1997) Tanzania Ministry of Health & AMMP Team, Dar es Salaam.***

## Distance to health facility

## Transportation to Health Facility

## The roads

## Patients deteriorate quickly

- For example, in Bangladesh, N= 199
- Children <6 years, progression to severe malaria
- 73% < 24 hours
- 83% < 48 hours

## Health Infrastructure in Navrongo, Ghana 

- Population 160,000
- 1  Hospital for District
- 3 Health Centres
- Traditional birth attendants and village health workers
- Traditional healers (240)
- first place of call in severe malaria (convulsion)
- 80% respondents

## Hospital and clinic experience of malaria in Navrongo, Ghana

- 50-60%  of  all outpatient cases
- 40% of admissions on paediatric ward
- 5- 25% die on admission
- Diagnosis based on history and clinical examination
- Treatment
- Chloroquine - primary drug
- SP and quinine - second-line drugs

## Essential Package of interventions for Home Management of Malaria

**Rectal Artesunate to **
**Prevent death**

**Prompt diagnosis & effective treatmen****t**

**Prevention of malaria **
**in **
**infancy  & pregnancy**

**Preventive Measures**
** ****Insecticide treated Bednets**

## The Prize

## Slide 71

## Indication

-    Artesunate Rectal Capsules are indicated for the initial management of acute malaria in patients who cannot take medication by mouth and for whom parenteral treatment is not available.