Slide 1

Thank you for the nice introduction. This is the topic I’ve been asked to speak about.

Slide 2

This is the problem I think that there is no need of such a long discussion to establish that this is a very severe condition and as we have understood previously instruments to interfere with progression of this disease are limited for the moment but are rapidly progressing.

Slide 3

Now, we can say that this is one of the most common human monogenic diseases. It’s frequent as you can see here and is characterised by progressive development and enlargement of focal cysts in both kidneys with disruption of normal renal tissue and accounts for 8-10% of ESRD cases in Western countries and as you can see here, costs for the disease are enormous.

Slide 4

We know that the renal cysts develop in a tiny fraction of the nephrons, cysts develop with an aberrant growth programme causing endless expansion and the severity of the disease is a direct consequence of the number of times and the frequency with which the cystogenic process occurs within the kidney over the life of the patient.

Slide 5

We know that there are two main conditions, probably there is also a third one but these are the two most common. PKD2 is less severe and is characterised by a slower progression of the disease as compared to PKD1 mutation and as has been anticipated before by professor Torres, it’s interesting that kidney function might be stable for a longer period of time before it starts to decline rapidly and this is a problem when you have to design clinical studies with drugs that might interfere with progression of the disease.

Slide 6

The severity of the disease is expression in large part not of a different rate of growth of cysts but most important because of an earlier development of cysts in these conditions as compared to this one. We were interested in understanding which were the structural components of the polycystic kidney that could help in predicting the progression of the disease in the long term and you know this is instrumental also in designing of intervention trials.

Slide 7

So we designed this explorative study to investigate the predictive power of structural quantification with respect to deterioration of renal function. We evaluated 13 patients with advanced-stage polycystic kidney and they were evaluated with not only CT scan to evaluate the kidney structure but also with a very precise estimate of glomerular infiltration rate by the iohexol plasma clearance. The same measurements were repeated after 6 months of frequent observation without any intervention.

Slide 8

By CT scan evaluation we identify according to automated classification of pixels based on image intensity statistics 4 components of the parenchyma.

Slide 9

One that is fat, one that is normal parenchyma, one that is cyst tissue and one is what we have called intermediate parenchyma.

Slide 10

That is something in between cyst and parenchymal tissue and that is probably the site where smaller cysts are localised that are still below the detection threshold of the CT scan evaluation. As we hypothesised, the intermediate parenchyma contains newly formed small cysts. This is an example of intermediate parenchyma in which there is a faintly contrast-enhanced parenchyma compared to no enhanced parenchyma that is the cyst and compared to fully enhanced parenchyma that is what is probably still intact kidney tissue. An interesting finding of this study was that we observed in 13 patients followed perspectively for 6 months that there was an inverse correlation between the change in the GFR and the change in the interstitial parenchyma, the intermediate parenchyma. If the intermediate parenchyma increases over time, you have a progressive reduction in the GFR and there is a strong association between the two variables. While we did not find an association or a significant correlation between the changes in the cyst volume and GFR decline. So, intermediate parenchyma seems to be quite predictive of progression of kidney function loss over time.

Slide 11

Just as an example we found that in a representative patient the largest cyst volume, the smallest intermediate parenchyma and the highest GFR were associated. So highest GFR but with smaller intermediate parenchyma despite a large amount of cyst volume. It seems that the intermediate parenchyma is parenchyma that progressively loses its function.

Slide 12

The finding indicates a possible new predictor of renal functional loss on the basis of renal structure evaluation. Our hypothesis is that the presence of diffuse changes in residual parenchyma, as detected by contrast-enhanced CT scan, may be deleterious for renal function. Of course, take this with caution because it’s a study in a limited number of patients and with limited follow up but the techniques that were used were very accurate.

Slide 13

So coming to our problem current therapies are inefficient in arresting or even slowing the rate of progressive loss of renal function in polycystic kidneys.

Slide 14

We have had a nice overview of a series of experimental models in which deferent interventions have been attempted. You see here many of them have been already encountered in different models also with different results. So far however, therapeutic interventions in humans were very, very limited.

Slide 15

It happened to us a few years ago to see a woman with a characteristic picture suggesting some benefit of somatostatin therapy in a polycystic kidney. This woman had an adenoma. Two year treatment with the somatostatin analogue octreotide for an adenoma of the pituitary gland and during this period there was no appreciable change in cyst areas with stable kidney function during the follow up. So this suggested that somatostatin could play some role in the disease progression of this woman taking this drug for another clinical reason that is a pituitary gland adenoma.

Slide 16

The hypothesis was that the possible inhibition of the enlargement of renal cysts by octreotide might have prevented further damage to the residual function of the kidney parenchyma, the intermediate parenchyma that we discussed before.

Slide 17

Now, we know that in polycystic kidney the polycystic cells respond to cAMP stimulation with cystic dilatation. If you expose the child to forskolin there is an aggravation of cAMP and an increase in fluid secretion driven in particular by active chloride secretion that accumulates in the cyst volume.

Slide 18

A possibility is that in animals, as well as in humans, the growth of the renal cyst is regulated by a process of continuous secretion and reabsorption. So you have an active chloride transport within the lumen of the cyst and when this overwhelms the passive reabsorption, you have a continuous increase in the volume of the cyst. But if you are able to inhibit secretion of fluid, you can change the balance between these two processes for instance by using somatostatin and this may inhibit fluid formation and induce shrinking of the renal cyst.

Slide 19

Of interest, somatostatin is able to inhibit the vasoactive intestinal peptide-stimulated chloride secretion by lowering cAMP accumulation on shark rectal gland cells.

Slide 20

We understood that before that the physiology of these animals is quite close to the human physiology and in experimental polycystic kidney there is a significant increase in cAMP levels compared to animals without the disease.

Slide 21

So cAMP seemed to be a possible target of therapeutic intervention in this disease as has been already previously discussed. Indeed consistently with this hypothesis is the evidence that the fluid of renal cysts of human disease in patients with different polycystic kidney force contains the lipophilic secretogogue/mitogen forskolin that stimulates cAMP formation in epithelial cells.

Slide 22

To summarise, there are serious evidence suggesting that cAMP plays a major role in cystogenesis by promoting fluid secretion and cell proliferation. cAMP stimulates a transepithelial movement of fluid across the polarised canine kidney cell monolayers. Activates chloride ion-driven fluid secretion via apical chloride channel in the renal collecting duct epithelium. Enhances the growth of canine kidney cell subconfluent monolayers, increases the proliferation of polycystic cells.

Slide 23

So somatostatin is a cylcopeptide that inhibits the secretion of growth hormone insulin and glucagon by binding to specific receptors and this is the clinical use for which this drug has been developed. There are different receptors for somatostatin and one of these Sst2 is represented in the human kidney and this is an example of the receptor.

Slide 24

High affinity Sst2 receptor for somatostatin are found in tubuli and vasa recta of the human kidney. There is a high expression for this receptor in the medulla but there is also some expression in the cortex that is specific for the tubuli and not for the glomeruli. Now in the polycystic kidney we have already understood from the previous presentation that there is a reduction in the influx calcium in the cells and this is associated with an activation of the adenylate cyclase with an increase in cAMP, cell proliferation and enhanced chloride secretion.

Slide 25

Somatostatin is able to specifically inhibit adenylate cyclase and this even in the setting of low calcium intracellular concentration it is able to prevent cAMP activation and thus inhibits cell proliferation and chloride secretion.

Slide 26

So by inhibiting cAMP generation somatostatin analogues could provide a novel therapeutic opportunity to modulate cystogenesis and to slow polycystic kidney disease progression.

Slide 27

To test this hypothesis we designed this randomised crossover study that was actually a pilot safety and efficacy study of long-acting somatostatin that is octreotide in 14 subjects, adult subjects with a polycystic kidney. They had diagnosis, echographic diagnosis of polycystic kidney. Mild to moderate renal insufficiency. We did not include subjects with normal kidney function and we did not include subjects with advanced kidney disease. After baseline evaluation including CT scan evaluation and GFR evaluation by iohexol plasma clearance in addition to other routine laboratory tests, patients were randomised to placebo or 6 months therapy with octreotide. Then the evaluations were repeated and they were crossed over to the other arms of treatment and then at 1 year of follow up the baseline evaluations were repeated. Sandostatin was given 40 mg every 28 days that is actually the dose used for a treatment of pituitary gland adenomas.

Slide 28

The structure of the kidney was evaluated again by serial CT scan imaging and with evaluation of the different components of the structure of the kidney, of the cystic kidney.

Slide 29

At baseline 9 patients had some degree of renal insufficiency, 7 and 1 patient respectively had micro and microalbuminuria and interestingly, overall on average 65% of the volume of the kidney of these subjects was occupied by radiologically detectable cysts. The volume was ranged up to 86% in one case.

Slide 30

Clinical characteristics of subjects at basal and after 6 months of treatment with placebo, main basal and after 6 months of treatment of somatostatin therapy were very well comparable with only a small reduction in GFR not significant following 6 months of somatostatin therapy.

Slide 31

This is the key finding of the study. During treatment with placebo there was as expected an increase in total kidney volume either in absolute value or in percent value of baseline. This increase was limited by somatostatin again either as total volume and absolute volume and percent volume and the difference over just 6 months in the rate of increase of total kidney volume was significant between placebo and somatostatin.

Slide 32

Of interest, when we evaluated the components of the kidney volume, we found that there was a small difference in cyst volume changes. There was a more evident difference in parenchymal volume change. The numbers are small and the differences are not significant so we must not overemphasise this finding. But I think that it is of some interest observing that in this case the volume is increasing while in this case the volume is decreasing maybe that over a longer period of treatment this difference may achieve significance. This is of course speculation.

Slide 33

So the portion of polycystic kidneys identified radiologically as parenchyma may contain many microscopic cysts below the detection threshold of CT scan evaluation. Somatostatin may lower the volume of these small cysts thus reducing the overall parenchymal volume consistently with what we discussed before.

Slide 34

If given early enough somatostatin, in addition to preventing small cyst formation and growth, might prevent the further loss of tissue and deterioration of renal function over time.

Slide 35

This was primarily a safety study and actually the drug was very well tolerated. We know the safety profile of this drug is good in other clinical settings. We had no information the safety profile of this drug in this typology of patients. Actually the only adverse event associated with the treatment that required somatostatin stop was asymptomatic cholelithiasis. This is an effect that is reported and that must be taken into consideration when you evaluate therapy with these agents in your polycystic patients. Then we have watery diarrhoea in three cases reversible and considered as mild and self limited. Then increases in liver transaminases that were not considered related to the study drug and actually recovered these abnormalities spontaneously and likely reflected the underlying liver disease.

Slide 36

In patients with polycystic kidney somatostatin therapy given for 6 months is safe and may slow renal volume increase largely by preventing the growth of the parenchymal volume. Whether this effect may prove renoprotective in the long-term however should be tested in additional trials of larger duration.

Slide 37

This is what are we addressing at this stage. We have designed what we could define a phase II, phase III study, it’s not of course this one as big a trial as the one that is ongoing described by Professor Torres, it’s somewhere in between a pilot study and a randomised clinical trial. 66 subjects are randomised to somatostatin or placebo and are followed for 3 years. At baseline, 1 and 3 years they have again evaluation of GFR and in this case magnetic resonance imaging for evaluating the structure of the kidney. The study’s coordinated by our clinical research centre – Institute in Bergamo Italy and these are 5 nephrology units in Italy involved in the study. The main outcome variable of the study will be the increase of kidney volume total and in its components and the rate of GFR decline.

Slide 38

To conclude an increased understanding of the genetic molecular and cellular mechanisms responsible for the involvement of polycystic kidney disease has laid out the foundations for the development of rational therapies. ADPKD clinical trials are now ongoing or in the early phases of implementation with octreotide, sirolimus, everolimus and tolvaptan.

Slide 39

These are the questions that should be addressed.
Will the drugs work equally well in both PKD1 and PKD2 individuals? Should only high risk individuals with specific volume: age ratios be targeted for therapy?
Will therapies need to be life-long or will short treatments provide long-term protection from cyst growth and expansion?
How early should treatment be given? And we had a question before on this issue.

Slide 40

Finally, another interesting observation. We have observed before that reduction in calcium concentration in one of the key determinants of cell proliferation. There are no drugs at the moment that directly effect calcium influx in these cells but I want to call to your attention this vine Tripterygium wilfordii. This is this kind of plant that has been used for centuries and centuries in the Chinese medicine to cure a series of diseases such as cancer, inflammation and autoimmune disease. Now we know that the active component triptolide induces polycystin-2-dependent intracellular calcium release and could be a valid therapeutic strategy for ADPKD. So at least for this specific condition in one case I believe that also what is called alternative medicine could have a role in the optimal care of our patients.

Slide 41

I thank you for your attention.

Slide 42

Chairman: Thank you Piero for this clear presentation and encouraging data. A major difference between the vasopressin antagonists and somatostatin analogues is the potential effect of somatostatin analogues on the liver polycystic disease could you summarise the available data showing that the somatostatin analogue may decrease also polycystic liver disease?

Dr Ruggenenti: This is a super question because you know we also have dialysis patients with big problems in the liver. I am aware of single case report suggesting a reduction in the volume of the cyst also in the liver. Now, we are processing the CT scan of 9 of our 14 patients including the scans that also had evidence of liver involvement. So I think that in 2-3 months we should have the answer also to this extremely important point.

Chairman: Additional comments on this point?

Dr Ruggenenti: Yes well just a comment. We do have a study published using octreotide in the PCK rats that shows that it is beneficial in the liver as well. We have an ongoing clinical trial on octreotide in patients with severe polycystic liver disease at Mayo which is focused on the liver but we don’t...

Question: You have an ongoing trial on liver polycystic?

Dr Ruggenenti: That’s correct we have a small trial that involves 46 patients, all the 46 patients have been treated now with some of them for over a year, some of them less than a year so we do hope to have data but we are focusing on the liver. We are going to look at the kidneys too but we are focusing on the liver.

Question: It would be nice to see whether there is a correlation between changes in the liver and changes in the kidney.

Chairman: Encouraging. The last question.

Question: A fascinating talk. You showed us data that parenchymal volume is going down with octreotide and you hope that these are the microcysts but at the same time you also showed that GFR is going down in the octreotide group. Is that not a bit disturbing with this new drug or do you think this is a temporary reversible hemodynamic effect?

Dr Ruggenenti: Yes a good question indeed. This is a reversible effect we have seen in our crossover studies and it’s described in other clinical conditions such as for instance, type 1 diabetes. The hypothesis is that somatostatin to some extent limits hyperfiltration that can be observed in these clinical conditions. So I think that this is the functional effect that in the short term such as for ACE inhibitors in the short term reduce GFR but that in theory we need the results of the trial in the long term it could be renoprotective. In any case it is a functional effect.

Chairman: Thank you very much doctor Ruggenenti